🕷️ Crawler Inspector

URL Lookup

Direct Parameter Lookup

Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 95 (from laksa134)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa095.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://www.factcheck.org/2024/02/study-largely-confirms-known-rare-covid-19-vaccine-side-effects/\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.factcheck.org/2024/02/study-largely-confirms-known-rare-covid-19-vaccine-side-effects/\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.factcheck.org\/2024\/02\/study-largely-confirms-known-rare-covid-19-vaccine-side-effects\/","crawl_time":1776305000,"first_indexed_time":1709071601,"http_code":200,"src_unparsed":"org,factcheck!www,\/2024\/02\/study-largely-confirms-known-rare-covid-19-vaccine-side-effects\/ s443","src_root_hash":"9637418184873233095","history_drop_reason":null,"meta_title":"Study Largely Confirms Known, Rare COVID-19 Vaccine Side Effects - FactCheck.org","meta_descriptions":[],"attrs_boilerpipe_text":"SciCheck Digest\nAn international study of around 99 million people confirmed known serious side effects of COVID-19 vaccination. It also identified a possible relationship between the first dose of the Moderna vaccine and a small risk of a neurological condition. Social media posts about the study left out information on the vaccines’ benefits and the rarity of the side effects.\nFull Story\nCOVID-19 vaccines — like all \nvaccines\n and other medical products — come with side effects, including \nserious side effects\n in rare cases. The vaccines were rolled out to protect people from a novel virus that has \nkilled\n millions of people globally and would likely have killed millions more without the arrival of the vaccines. There is a broad consensus from\nexperts\nand\ngovernmental\nhealth\nagencies\nthat the benefits of COVID-19 vaccination outweigh the risks.\nResearchers have \nscrutinized\n the COVID-19 vaccines’ safety and continue to do so. A \nstudy\n published Feb. 12 in the journal Vaccine reported on an international group of more than 99 million people who received COVID-19 vaccines, primarily finding links to known rare side effects. The study largely focused on the Pfizer\/BioNTech and Moderna vaccines, which have been \nwidely given\n in the U.S., as well as the AstraZeneca vaccine, which was \nnever authorized\n in the U.S.\n“What we take away, is that the Covid-19 vaccination campaigns have been very effective in preventing severe disease,” study co-author \nAnders Hviid\n, head of the department of epidemiology research at the Statens Serum Institut in Denmark, told us in an email. “The few serious side effects that we have observed in this and other studies have been rare.”\nMany popular posts on social media have shared results from the study, some lacking the context that the identified \nhealth problems\nare\nrare\n, that\nmost\naren’t\nnew\nand that the vaccines have proven benefits. Various posts made unfounded claims, stating or implying that people\nshould not\nhave\nreceived\nthe\nvaccines\n, that the risks\noutweigh\nthe benefits or that the \nrisk\nof the rare side effects is\ngreater\nthan was reported in the study.\n“Hundreds of millions of people were used as lab rats and now the truth that WE ALL ALREADY KNEW can no longer be denied,” said one popular \npost\n, referring to the vaccines as “experimental” and “UNTESTED.” The post shared a screenshot of the headline of a New York Post \narticle\n about the new study, which read, “COVID vaccines linked to slight increases in heart, brain, blood disorders: study.”\n“This thing was forced on people who faced almost no risk from Covid,” said another widely read\npost\n. “It is completely unacceptable.” The post shared statistics from the paper without making it clear that serious health problems after vaccination were rare and that risk varied by vaccine type and dose.\nThe Vaccine study confirmed that the Moderna and Pfizer\/BioNTech vaccines are linked in rare cases to myocarditis and pericarditis, conditions\ninvolving\ninflammation of the heart muscle and lining. The rate of myocarditis was most elevated after the second dose of the Moderna vaccine. Myocarditis risk — which is greatest in men in their late teens and early twenties — was \nidentified\nvia vaccine safety monitoring and first reported in 2021. Based on the current evidence, the \nCDC\nsays, the benefit of vaccination outweighs the risk of these conditions, which improve for most people after medical treatment and rest.\nThe study confirmed neurological and blood clotting conditions associated with the AstraZeneca vaccine. In the U.S., these \nproblems\n were \nlinked\n to the Johnson & Johnson vaccine, contributing to this vaccine no longer being recommended or available.\nThe study also identified a new possible safety signal indicating a potential link between the first dose of the Moderna and AstraZeneca vaccines and rare neurological conditions. This included an association between the first doses of the vaccines and acute disseminated encephalomyelitis, or ADEM, an autoimmune\ncondition\nthat\ncauses\ninflammation of the brain and spinal cord.\nHviid emphasized that the researchers only saw these neurological events after first doses of the two vaccines. “We did not see these signals following further doses of these two Covid-19 vaccines, nor did we see them after any dose of the Pfizer\/BioNTech vaccine which has been more widely used,” he said.\n“We are also talking about very rare events,” Hviid continued. “As an example, the association between the first dose of Moderna and acute inflammation of the brain and spine would, if causal, correspond to 1 case per 1.75 million vaccinated. It is only due to the sheer scale of our study, that we have been able to identify this minute potential risk.”\nStudy Bolsters the Evidence Serious COVID-19 Vaccine Side Effects Are Rare\nThe Vaccine \nstudy\n drew on national or regional health records from eight countries with institutions participating in the \nGlobal Vaccine Data Network\n, an international group that studies vaccine safety. The researchers analyzed health outcomes after around 184 million doses of the Pfizer\/BioNTech vaccine, 36 million doses of the Moderna vaccine and 23 million doses of the AstraZeneca vaccine. \nThe researchers focused on 13 health problems that either had a known association with vaccination or for which there was some rationale to investigate whether there was an association. To determine whether the health problems were associated with vaccination, they compared the expected rates of the health problems — or the number of health events that should occur based on background rates in the regions studied — with the number of events they observed in the 42 days after vaccination.\n“This study confirms the primary already detected and validated side effects established by previous literature,” \nJeffrey S. Morris\n, director of the division of biostatistics at the University of Pennsylvania’s Perelman School of Medicine, told us via email, referring to the rare heart conditions associated with the Moderna and Pfizer\/BioNTech vaccines, as well as the rare conditions associated with the AstraZeneca and Johnson & Johnson vaccines. \nMorris said that findings on ADEM — the rare autoimmune neurological condition linked to first doses of the Moderna and AstraZeneca vaccines — “might be a new safety signal.” \nADEM \ninvolves\n inflammation to the brain and spinal cord, arising most often in children following an infectious illness. It has a \nsudden onset\n and typically eventually improves, with a full recovery in many, although not all, cases.\nAfter the first dose of the Moderna vaccine, researchers observed seven ADEM cases, when they expected two. As we’ve said, Hviid calculated the rate of this side effect — if ultimately shown to be related to vaccination — to be 1 in 1.75 million following the first dose of the Moderna vaccine. \nThe data show “this was indeed an EXTREMELY rare adverse event,” Morris said, referring to ADEM. “It is understandable at this incidence rate why it may not have been detected before now, and why a study with 99 million participants like this is important to find even the most rare serious adverse events that are potential minority harm risks of these vaccines.”\nThe authors of the study wrote that more research is needed into ADEM following COVID-19 vaccination, saying that “the number of cases of this rare event were small and the confidence interval wide, so results should be interpreted with caution and confirmed in future studies.” The authors also wrote that neurological \nevents\n have been found to occur at a much higher rate after COVID-19 than after COVID-19 vaccination.\nThe study means that “early warning systems are solid,” said \nMarc Veldhoen\n, an immunologist at the Instituto de Medicina Molecular João Lobo Antunes in Portugal, in a \npost\n on X, formerly known as Twitter. “To avoid any adverse reaction is not possible, but, identifying those at higher risk may be possible.”\nIdentifying those at greater risk of side effects can help guide decisions on which vaccines to recommend and what problems doctors should watch for in their patients.\nEditor’s note: SciCheck’s articles providing accurate health information and correcting health misinformation are made possible by a grant from the Robert Wood Johnson Foundation. The foundation has\nno control\nover FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation.\nSources\n“\nHow do we know vaccines are safe?\n” FactCheck.org. Updated 8 Jul 2021.\n“\nSelected Adverse Events Reported after COVID-19 Vaccination\n.” CDC website. Updated 12 Sep 2023.\nYandell, Kate. “\nTucker Carlson Video Spreads Falsehoods on COVID-19 Vaccines, WHO Accord\n.” FactCheck.org. 13 Jan 2024.\n“\nSafety of COVID-19 Vaccines\n.” CDC website. 3 Nov 2023.\n“\nHow safe are the COVID-19 vaccines?\n” FactCheck.org. Updated 17 May 2022.\nFaksova, K. et al. “\nCOVID-19 Vaccines and Adverse Events of Special Interest: A Multinational Global Vaccine Data Network (GVDN) Cohort Study of 99 Million Vaccinated Individuals\n.” Vaccine. 12 Feb 2024.\nCOVID Data Tracker. “\nCOVID-19 Vaccinations in the United States\n.” CDC website. Updated 11 May 2023.\nLiu, Angus. “\nAstraZeneca withdraws US COVID vaccine application, shifts focus to antibody treatments\n.” Fierce Pharma. 10 Nov 2022.\nHviid, Anders. Email with FactCheck.org. 22 Feb 2024.\nTheBlaze. “\nBlood clots, neurological disorders, and swollen hearts: Multinational study on COVID vaccines paints a damning picture\n.” Facebook. 20 Feb 2024.\nDr. Anthony G. Jay (@anthonygjay). “\nI post a lot of vids but rarely PLUG them WATCH my YouTube vid on this – it’s 6 minutes – before it gets taken down 🤐\n.” Instagram. 20 Feb 2024.\nbikinibottom_fish 🐟 (@bikinibottom_fish). “\nGlobal Study Links COVID-19 Vaccines to Heart and Brain Issues!\n” Instagram. 20 Feb 2024.\nPatrioticBabe 🇺🇸 (@babedoesthenews). “\n❗️\n.” Instagram. 20 Feb 2024.\nRASPY RAWLS (@raspy_rawls2). “\n… We told yall not to take that shyt but hey wat dew we know 🤷🏾‍♂️ …\n .” Instagram. 20 Feb 2024.\nJaimee Michell (@thegaywhostrayed). “\nI want to know if you think Trump holds any blame, and if not, why not? COMMENT your thoughts BELOW!\n” Instagram. 20 Feb 2024.\nLiberty Counsel (@libertycounsel). “\n… \n“Based on ‘conservative assumptions,’ the estimated harms of the COVID-19 mRNA vaccines ‘greatly outweigh the rewards,’ the article stated, noting that ‘for every life saved, there were nearly 14 times more deaths caused by the modified mRNA injections.’” …\n” Instagram. 20 Feb 2024.\nShemeka Michelle (@\ntheshemekamichelle\n). “\nRemember when they called them “rare” breakthrough cases? Yeah, me too. #slight\n.” Instagram. 20 Feb 2024.\nMal’aki (@awake.the.mind). “\n‘Slight’ will turn to ‘significant’ soon enough. We tried to warn you all but we’re just crazy conspiracy theorists\n.” Instagram. 20 Feb 2024.\nSteinbuch, Yaron. “\nCOVID vaccines linked to slight increases in heart, brain, blood disorders: study\n.” New York Post. 20 Feb 2024.\nVogel, Gretchen and Couzin-Frankel, Jennifer. “\nIsrael reports link between rare cases of heart inflammation and COVID-19 vaccination in young men\n.” Science. 1 Jun 2021.\nRobertson, Lori and Kiely, Eugene. “\nQ&A on the Rare Clotting Events That Caused the J&J Pause\n.” FactCheck.org. Updated 6 May 2022.\nKahn, Ilana. “\nAcute Transverse Myelitis and Acute Disseminated Encephalomyelitis\n.” Pediatrics in Review. 1 Jul 2020.\nMorgan, Hannah J. et al. “\nAcute Disseminated Encephalomyelitis and Transverse Myelitis Following COVID-19 Vaccination – A Self-Controlled Case Series Analysis\n.” Vaccine. 12 Feb 2024. \n“\nGlobal COVID Vaccine Safety (GCoVS)\n.” Global Vaccine Data Network website. Accessed 23 Feb 2024.\nMorris, Jeffrey S. Email with FactCheck.org. 22 Feb 2024.\nFrontera, Jennifer A. et al. “\nNeurological Events Reported after COVID-19 Vaccines: An Analysis of VAERS\n.” Annals of Neurology. 2 Mar 2022.\nMarc Veldhoen (@Marc_Veld). “\nCOVID-19 vaccines and adverse events of special interest: A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals Anything in those anti-vax stories about large scale damage and deaths due to vaccines? No. …\n” X. 19 Feb 2024.","attrs_markdown":"[Skip to main content](https:\/\/www.factcheck.org\/2024\/02\/study-largely-confirms-known-rare-covid-19-vaccine-side-effects\/#main)\n\n[FactCheck.org®](https:\/\/www.factcheck.org\/)\n\nA Project of The Annenberg Public Policy Center\n\n[![Become a Facebook fan](https:\/\/cdn.factcheck.org\/UploadedFiles\/fc-icon-facebook-mini.png)](https:\/\/www.facebook.com\/factcheck.org)\n\n[![Follow us on Twitter](https:\/\/cdn.factcheck.org\/UploadedFiles\/x-icon-logo-black.png)](https:\/\/www.x.com\/factcheckdotorg)\n\n[![Get the RSS feed](https:\/\/cdn.factcheck.org\/UploadedFiles\/fc-icon-rss.png)](https:\/\/www.factcheck.org\/feed\/)\n\n[![Follow on Insta](https:\/\/cdn.factcheck.org\/UploadedFiles\/fc-icon-instagram-1.png)](https:\/\/www.instagram.com\/factcheckorg\/)\n\n[![Sign up for the email newsletter](https:\/\/cdn.factcheck.org\/UploadedFiles\/fc-icon-email.png)](https:\/\/www.factcheck.org\/subscribe\/)\n\n[![Help us hold politicians accountable. ](https:\/\/cdn.factcheck.org\/UploadedFiles\/fc-icon-donate.png)](https:\/\/giving.aws.cloud.upenn.edu\/?fastStart=simpleForm&program=ANS&fund=602014)\n\nSciCheck’s COVID-19\/Vaccination Project\n\n[Learn More](https:\/\/www.factcheck.org\/covid-misconceptions)\n\n[FactCheck.org®](https:\/\/www.factcheck.org\/)\n\n- [Home](https:\/\/www.factcheck.org\/ \"Home\")\n- [Articles](https:\/\/www.factcheck.org\/2024\/02\/study-largely-confirms-known-rare-covid-19-vaccine-side-effects\/ \"Articles\")\n  - [FactCheck Posts](https:\/\/www.factcheck.org\/the-factcheck-wire\/ \"FactCheck Posts\")\n  - [SciCheck](https:\/\/www.factcheck.org\/scicheck\/ \"SciCheck\")\n  - [En Español](https:\/\/www.factcheck.org\/es\/en-espanol\/ \"En Español\")\n  - [Project 2025 series](https:\/\/www.factcheck.org\/issue\/project-2025-series\/ \"Project 2025 series\")\n  - [Debunking Viral Claims](https:\/\/www.factcheck.org\/fake-news\/ \"Debunking Viral Claims\")\n- [Ask a Question](https:\/\/www.factcheck.org\/2024\/02\/study-largely-confirms-known-rare-covid-19-vaccine-side-effects\/ \"Ask a Question\")\n  - [Ask FactCheck](https:\/\/www.factcheck.org\/askfactcheck\/ \"Ask FactCheck\")\n  - [Ask SciCheck](https:\/\/www.factcheck.org\/askscicheck\/ \"Ask SciCheck\")\n- [Donate](https:\/\/giving.aws.cloud.upenn.edu\/fund?fastStart=simpleForm&program=ANS&fund=602014 \"Donate\")\n- [Topics](https:\/\/www.factcheck.org\/2024\/02\/study-largely-confirms-known-rare-covid-19-vaccine-side-effects\/ \"Topics\")\n  - [President Trump](https:\/\/www.factcheck.org\/person\/donald-trump\/ \"President Trump\")\n  - [Robert F. Kennedy Jr.](https:\/\/www.factcheck.org\/person\/robert-f-kennedy-jr\/ \"Robert F. Kennedy Jr.\")\n  - [immigration](https:\/\/www.factcheck.org\/issue\/immigration\/ \"immigration\")\n  - [climate change](https:\/\/www.factcheck.org\/issue\/climate-change\/ \"climate change\")\n  - [coronavirus](https:\/\/www.factcheck.org\/issue\/coronavirus\/ \"coronavirus\")\n  - [tariffs](https:\/\/www.factcheck.org\/issue\/tariffs\/ \"tariffs\")\n  - [View All](https:\/\/www.factcheck.org\/archives\/ \"View All\")\n- [About Us](https:\/\/www.factcheck.org\/2024\/02\/study-largely-confirms-known-rare-covid-19-vaccine-side-effects\/ \"About Us\")\n  - [Our Mission](https:\/\/www.factcheck.org\/about\/our-mission\/ \"Our Mission\")\n  - [Our Process](https:\/\/www.factcheck.org\/our-process\/ \"Our Process\")\n  - [Our Funding](https:\/\/www.factcheck.org\/our-funding\/ \"Our Funding\")\n  - [Our Staff](https:\/\/www.factcheck.org\/our-staff\/ \"Our Staff\")\n  - [Undergraduate Fellows](https:\/\/www.factcheck.org\/undergraduate-fellows\/ \"Undergraduate Fellows\")\n  - [Awards](https:\/\/www.factcheck.org\/awards\/ \"Awards\")\n  - [Request a Correction](https:\/\/www.factcheck.org\/request-a-correction\/ \"Request a Correction\")\n  - [Contact Us](https:\/\/www.factcheck.org\/about\/contact-us\/ \"Contact Us\")\n- [Search](https:\/\/www.factcheck.org\/search\/ \"Search\")\n- [More](https:\/\/www.factcheck.org\/2024\/02\/study-largely-confirms-known-rare-covid-19-vaccine-side-effects\/ \"More\")\n  - [Viral Claims](https:\/\/www.factcheck.org\/hot-topics\/ \"Viral Claims\")\n  - [Newsletter](https:\/\/www.factcheck.org\/subscribe\/ \"Newsletter\")\n  - [Instagram](https:\/\/www.instagram.com\/factcheckorg\/ \"Instagram\")\n  - [Threads](https:\/\/www.threads.net\/@factcheckorg \"Threads\")\n  - [YouTube](https:\/\/www.youtube.com\/factcheckdotorg \"YouTube\")\n  - [TikTok](https:\/\/www.tiktok.com\/@factcheckorg \"TikTok\")\n  - [Facebook](https:\/\/www.facebook.com\/factcheck.org \"Facebook\")\n  - [X](https:\/\/twitter.com\/factcheckdotorg \"X\")\n  - [FactCheck On the Air](https:\/\/www.factcheck.org\/on-the-air\/ \"FactCheck On the Air\")\n\n[Debunking Viral Claims](https:\/\/www.factcheck.org\/fake-news\/) › [FactCheck Posts](https:\/\/www.factcheck.org\/the-factcheck-wire\/) › [SciCheck](https:\/\/www.factcheck.org\/scicheck\/)\n\n# Study Largely Confirms Known, Rare COVID-19 Vaccine Side Effects\nBy [Kate Yandell](https:\/\/www.factcheck.org\/author\/kate-yandell\/ \"Posts by Kate Yandell\")\n\nPosted on February 27, 2024\n***\nThis article is available in both English and Español\n\n## SciCheck Digest\nAn international study of around 99 million people confirmed known serious side effects of COVID-19 vaccination. It also identified a possible relationship between the first dose of the Moderna vaccine and a small risk of a neurological condition. Social media posts about the study left out information on the vaccines’ benefits and the rarity of the side effects.\n\n![](https:\/\/cdn.factcheck.org\/UploadedFiles\/rwjf-icon-vaccination-04%402x.png)\n\nHow safe are the COVID-19 vaccines?\n\n[How safe are the COVID-19 vaccines?](https:\/\/www.factcheck.org\/scicheck_digest\/how-safe-are-the-vaccines\/)\n\nMore than [half a billion](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/safety-of-vaccines.html) doses of COVID-19 vaccines have now been administered in the U.S. and only a few, very rare, safety concerns have emerged. The vast majority of people experience only minor, temporary side effects such as pain at the injection site, fatigue, headache, or muscle pain — or no side effects at all. As the Centers for Disease Control and Prevention has [said](https:\/\/archive.md\/fG255), these vaccines “have undergone and will continue to undergo the most intensive safety monitoring in U.S. history.”\n\nA small number of severe allergic reactions known as anaphylaxis, which are expected with any vaccine, [have](https:\/\/www.cdc.gov\/mmwr\/volumes\/70\/wr\/mm7004e1.htm?s_cid=mm7004e1_w) [occurred](https:\/\/www.cdc.gov\/mmwr\/volumes\/70\/wr\/mm7002e1.htm?s_cid=mm7002e1_w) with the authorized and approved COVID-19 vaccines. Fortunately, these reactions are rare, typically occur within minutes of inoculation and can be treated. Approximately 5 per million people vaccinated have experienced anaphylaxis after a COVID-19 vaccine, [according](https:\/\/archive.ph\/ZnaGT) to the CDC.\n\nTo make sure serious allergic reactions can be identified and treated, all people receiving a vaccine [should be observed](https:\/\/www.cdc.gov\/vaccines\/covid-19\/info-by-product\/pfizer\/anaphylaxis-management.html) for 15 minutes after getting a shot, and anyone who has experienced anaphylaxis or had any kind of immediate allergic reaction to any vaccine or injection in the past should be monitored for a half hour. People who have had a serious allergic reaction to a previous dose or one of the [vaccine](https:\/\/www.fda.gov\/media\/144414\/download) [ingredients](https:\/\/www.fda.gov\/media\/144638\/download) [should not](https:\/\/www.fda.gov\/media\/144638\/download) be immunized. Also, those who shouldn’t receive one type of COVID-19 vaccine should be monitored for 30 minutes after receiving a different type of vaccine.\n\nThere is [evidence](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/myocarditis.html) that the Pfizer\/BioNTech and Moderna mRNA vaccines may rarely cause inflammation of the heart muscle (myocarditis) or of the surrounding lining (pericarditis), particularly in male adolescents and young adults.\n\nBased on [data](https:\/\/jamanetwork.com\/journals\/jama\/fullarticle\/2788346) collected through August 2021, the reporting rates of either condition in the U.S. are highest in males 16 to 17 years old after the second dose (105.9 cases per million doses of the Pfizer\/BioNTech vaccine), followed by 12- to 15-year-old males (70.7 cases per million). The rate for 18- to 24-year-old males was 52.4 cases and 56.3 cases per million doses of Pfizer\/BioNTech and Moderna vaccines, respectively.\n\nHealth officials have [emphasized](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/myocarditis.html) that vaccine-related myocarditis and pericarditis cases are rare and the benefits of vaccination still outweigh the risks. Early evidence [suggests](https:\/\/jamanetwork.com\/journals\/jama\/fullarticle\/2788346) these myocarditis cases are less severe than typical ones. The CDC has also [noted](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/myocarditis.html) that most patients who were treated “responded well to medicine and rest and felt better quickly.”\n\nThe Johnson & Johnson vaccine has been linked to an [increased risk](https:\/\/archive.ph\/ZnaGT) of rare blood clots combined with low levels of blood platelets, especially in women ages [30 to 49](https:\/\/www.cdc.gov\/vaccines\/acip\/meetings\/downloads\/slides-2021-12-16\/02-COVID-See-508.pdf). Early symptoms of the condition, which is known as thrombosis with thrombocytopenia syndrome, or TTS, can appear as late as three weeks after vaccination and [include](https:\/\/www.cdc.gov\/vaccines\/covid-19\/clinical-considerations\/covid-19-vaccines-us.html#considerations-Janssen) severe or persistent headaches or blurred vision, leg swelling, and easy bruising or tiny blood spots under the skin outside of the injection site.\n\nAccording to the CDC, TTS has [occurred](https:\/\/archive.ph\/ZnaGT) in around 4 people per million doses administered. As of [early April](https:\/\/archive.ph\/vx2mJ), the syndrome has been confirmed in 60 cases, including nine deaths, after more than 18.6 million doses of the J\\&J vaccine. Although TTS remains rare, because of the availability of mRNA vaccines, which are not associated with this serious side effect, the FDA on May 5 [limited authorized use](https:\/\/perma.cc\/T7ZA-EF28) of the J\\&J vaccine to adults who either couldn’t get one of the other authorized or approved COVID-19 vaccines because of medical or access reasons, or only wanted a J\\&J vaccine for protection against the disease. Several months earlier, [on Dec. 16, 2021](https:\/\/www.cdc.gov\/media\/releases\/2021\/s1216-covid-19-vaccines.html), the CDC had recommended the Pfizer\/BioNTech and Moderna shots over J\\&J’s.\n\nThe J\\&J vaccine has also been linked to an [increased risk](https:\/\/archive.ph\/ZnaGT) of Guillain-Barré Syndrome, a rare disorder in which the immune system attacks nerve cells. [Most people](https:\/\/www.cdc.gov\/vaccinesafety\/concerns\/guillain-barre-syndrome.html) who develop GBS fully recover, although some have permanent nerve damage and the condition can be fatal.\n\nSafety surveillance data [suggest](https:\/\/jamanetwork.com\/journals\/jamanetworkopen\/fullarticle\/2791533) that compared with the mRNA vaccines, which have not been linked to GBS, the J\\&J vaccine is associated with 15.5 additional GBS cases per million doses of vaccine in the three weeks following vaccination. Most reported cases following J\\&J vaccination have occurred in men 50 years old and older.\n\n[Link to this](https:\/\/www.factcheck.org\/scicheck_digest\/how-safe-are-the-vaccines\/)\n***\n## Full Story\nCOVID-19 vaccines — like all [vaccines](https:\/\/www.factcheck.org\/scicheck_digest\/how-do-we-know-vaccines-are-safe\/) and other medical products — come with side effects, including [serious side effects](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/adverse-events.html) in rare cases. The vaccines were rolled out to protect people from a novel virus that has [killed](https:\/\/www.factcheck.org\/2024\/01\/scicheck-tucker-carlson-video-spreads-falsehoods-on-covid-19-vaccines-who-accord\/) millions of people globally and would likely have killed millions more without the arrival of the vaccines. There is a broad consensus from [experts](https:\/\/www.who.int\/news-room\/questions-and-answers\/item\/coronavirus-disease-\\(covid-19\\)-vaccines) and [governmental](https:\/\/www.fda.gov\/news-events\/press-announcements\/fda-takes-action-updated-mrna-covid-19-vaccines-better-protect-against-currently-circulating) health [agencies](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/safety-of-vaccines.html) that the benefits of COVID-19 vaccination outweigh the risks.\n\nResearchers have [scrutinized](https:\/\/www.factcheck.org\/scicheck_digest\/how-safe-are-the-vaccines\/) the COVID-19 vaccines’ safety and continue to do so. A [study](https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0264410X24001270) published Feb. 12 in the journal Vaccine reported on an international group of more than 99 million people who received COVID-19 vaccines, primarily finding links to known rare side effects. The study largely focused on the Pfizer\/BioNTech and Moderna vaccines, which have been [widely given](https:\/\/covid.cdc.gov\/covid-data-tracker\/#vaccinations_vacc-people-booster-percent-pop5) in the U.S., as well as the AstraZeneca vaccine, which was [never authorized](https:\/\/www.fiercepharma.com\/pharma\/astrazeneca-withdraws-us-covid-vaccine-application-focus-shifts-antibody-treatments) in the U.S.\n\n![](https:\/\/cdn.factcheck.org\/UploadedFiles\/SciCHECKsquare_4-161x145.png)\n\n“What we take away, is that the Covid-19 vaccination campaigns have been very effective in preventing severe disease,” study co-author [Anders Hviid](https:\/\/en.ssi.dk\/about-us\/contact\/employees\/a\/anders-peter-hviid-aii), head of the department of epidemiology research at the Statens Serum Institut in Denmark, told us in an email. “The few serious side effects that we have observed in this and other studies have been rare.”\n\nMany popular posts on social media have shared results from the study, some lacking the context that the identified [health problems](https:\/\/perma.cc\/J8CM-UD26) are [rare](https:\/\/perma.cc\/Z54H-ESKX), that [most](https:\/\/perma.cc\/V55U-8326) aren’t [new](https:\/\/perma.cc\/B93J-XVC5) and that the vaccines have proven benefits. Various posts made unfounded claims, stating or implying that people [should not](https:\/\/perma.cc\/ST9S-CCAC) have [received](https:\/\/perma.cc\/6EX7-CFNP) the [vaccines](https:\/\/perma.cc\/7TKY-2YH7), that the risks [outweigh](https:\/\/perma.cc\/8QN4-7LVM) the benefits or that the [risk](https:\/\/perma.cc\/D4UM-WH8C) of the rare side effects is [greater](https:\/\/perma.cc\/MGK4-Y6CV) than was reported in the study.\n\n“Hundreds of millions of people were used as lab rats and now the truth that WE ALL ALREADY KNEW can no longer be denied,” said one popular [post](https:\/\/perma.cc\/6EX7-CFNP), referring to the vaccines as “experimental” and “UNTESTED.” The post shared a screenshot of the headline of a New York Post [article](https:\/\/perma.cc\/2VYG-GB9X) about the new study, which read, “COVID vaccines linked to slight increases in heart, brain, blood disorders: study.”\n\n“This thing was forced on people who faced almost no risk from Covid,” said another widely read [post](https:\/\/perma.cc\/4SP3-55WN). “It is completely unacceptable.” The post shared statistics from the paper without making it clear that serious health problems after vaccination were rare and that risk varied by vaccine type and dose.\n\nThe Vaccine study confirmed that the Moderna and Pfizer\/BioNTech vaccines are linked in rare cases to myocarditis and pericarditis, conditions [involving](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/adverse-events.html) inflammation of the heart muscle and lining. The rate of myocarditis was most elevated after the second dose of the Moderna vaccine. Myocarditis risk — which is greatest in men in their late teens and early twenties — was [identified](https:\/\/www.science.org\/content\/article\/israel-reports-link-between-rare-cases-heart-inflammation-and-covid-19-vaccination) via vaccine safety monitoring and first reported in 2021. Based on the current evidence, the [CDC](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/adverse-events.html) says, the benefit of vaccination outweighs the risk of these conditions, which improve for most people after medical treatment and rest.\n\nThe study confirmed neurological and blood clotting conditions associated with the AstraZeneca vaccine. In the U.S., these [problems](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/adverse-events.html) were [linked](https:\/\/www.factcheck.org\/2021\/04\/scicheck-qa-on-the-rare-clotting-events-that-caused-the-jj-pause\/) to the Johnson & Johnson vaccine, contributing to this vaccine no longer being recommended or available.\n\nThe study also identified a new possible safety signal indicating a potential link between the first dose of the Moderna and AstraZeneca vaccines and rare neurological conditions. This included an association between the first doses of the vaccines and acute disseminated encephalomyelitis, or ADEM, an autoimmune [condition](https:\/\/publications.aap.org\/pediatricsinreview\/article-abstract\/41\/7\/313\/35435\/Acute-Transverse-Myelitis-and-Acute-Disseminated) that [causes](https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0264410X24001269) inflammation of the brain and spinal cord.\n\nHviid emphasized that the researchers only saw these neurological events after first doses of the two vaccines. “We did not see these signals following further doses of these two Covid-19 vaccines, nor did we see them after any dose of the Pfizer\/BioNTech vaccine which has been more widely used,” he said.\n\n“We are also talking about very rare events,” Hviid continued. “As an example, the association between the first dose of Moderna and acute inflammation of the brain and spine would, if causal, correspond to 1 case per 1.75 million vaccinated. It is only due to the sheer scale of our study, that we have been able to identify this minute potential risk.”\n\n## Study Bolsters the Evidence Serious COVID-19 Vaccine Side Effects Are Rare\nThe Vaccine [study](https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0264410X24001270#s0095) drew on national or regional health records from eight countries with institutions participating in the [Global Vaccine Data Network](https:\/\/globalvaccinedatanetwork.org\/ourwork\/global-covid-vaccine-safety-gcovs), an international group that studies vaccine safety. The researchers analyzed health outcomes after around 184 million doses of the Pfizer\/BioNTech vaccine, 36 million doses of the Moderna vaccine and 23 million doses of the AstraZeneca vaccine.\n\n![](https:\/\/cdn.factcheck.org\/UploadedFiles\/vaccine-400x267-1-1.jpeg)\n\nOrathai *\/* [stock.adobe.com](https:\/\/stock.adobe.com\/)\n\nThe researchers focused on 13 health problems that either had a known association with vaccination or for which there was some rationale to investigate whether there was an association. To determine whether the health problems were associated with vaccination, they compared the expected rates of the health problems — or the number of health events that should occur based on background rates in the regions studied — with the number of events they observed in the 42 days after vaccination.\n\n“This study confirms the primary already detected and validated side effects established by previous literature,” [Jeffrey S. Morris](https:\/\/www.dbei.med.upenn.edu\/bio\/jeffrey-s-morris-phd), director of the division of biostatistics at the University of Pennsylvania’s Perelman School of Medicine, told us via email, referring to the rare heart conditions associated with the Moderna and Pfizer\/BioNTech vaccines, as well as the rare conditions associated with the AstraZeneca and Johnson & Johnson vaccines.\n\nMorris said that findings on ADEM — the rare autoimmune neurological condition linked to first doses of the Moderna and AstraZeneca vaccines — “might be a new safety signal.”\n\nADEM [involves](https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0264410X24001269) inflammation to the brain and spinal cord, arising most often in children following an infectious illness. It has a [sudden onset](https:\/\/publications.aap.org\/pediatricsinreview\/article-abstract\/41\/7\/313\/35435\/Acute-Transverse-Myelitis-and-Acute-Disseminated) and typically eventually improves, with a full recovery in many, although not all, cases.\n\nAfter the first dose of the Moderna vaccine, researchers observed seven ADEM cases, when they expected two. As we’ve said, Hviid calculated the rate of this side effect — if ultimately shown to be related to vaccination — to be 1 in 1.75 million following the first dose of the Moderna vaccine.\n\nThe data show “this was indeed an EXTREMELY rare adverse event,” Morris said, referring to ADEM. “It is understandable at this incidence rate why it may not have been detected before now, and why a study with 99 million participants like this is important to find even the most rare serious adverse events that are potential minority harm risks of these vaccines.”\n\nThe authors of the study wrote that more research is needed into ADEM following COVID-19 vaccination, saying that “the number of cases of this rare event were small and the confidence interval wide, so results should be interpreted with caution and confirmed in future studies.” The authors also wrote that neurological [events](https:\/\/pubmed.ncbi.nlm.nih.gov\/35233819\/) have been found to occur at a much higher rate after COVID-19 than after COVID-19 vaccination.\n\nThe study means that “early warning systems are solid,” said [Marc Veldhoen](https:\/\/imm.medicina.ulisboa.pt\/investigation\/laboratories\/marc-veldhoen-lab\/#intro), an immunologist at the Instituto de Medicina Molecular João Lobo Antunes in Portugal, in a [post](https:\/\/perma.cc\/5JKF-QEKL) on X, formerly known as Twitter. “To avoid any adverse reaction is not possible, but, identifying those at higher risk may be possible.”\n\nIdentifying those at greater risk of side effects can help guide decisions on which vaccines to recommend and what problems doctors should watch for in their patients.\n***\n*Editor’s note: SciCheck’s articles providing accurate health information and correcting health misinformation are made possible by a grant from the Robert Wood Johnson Foundation. The foundation has [no control](https:\/\/www.factcheck.org\/2021\/04\/scicheck-and-our-committment-to-transparency\/) over FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation.*\n\n## Sources\n“[How do we know vaccines are safe?](https:\/\/www.factcheck.org\/scicheck_digest\/how-do-we-know-vaccines-are-safe\/)” FactCheck.org. Updated 8 Jul 2021.\n\n“[Selected Adverse Events Reported after COVID-19 Vaccination](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/adverse-events.html).” CDC website. Updated 12 Sep 2023.\n\nYandell, Kate. “[Tucker Carlson Video Spreads Falsehoods on COVID-19 Vaccines, WHO Accord](https:\/\/www.factcheck.org\/2024\/01\/scicheck-tucker-carlson-video-spreads-falsehoods-on-covid-19-vaccines-who-accord\/).” FactCheck.org. 13 Jan 2024.\n\n“[Safety of COVID-19 Vaccines](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/safety-of-vaccines.html).” CDC website. 3 Nov 2023.\n\n“[How safe are the COVID-19 vaccines?](https:\/\/www.factcheck.org\/scicheck_digest\/how-safe-are-the-vaccines\/)” FactCheck.org. Updated 17 May 2022.\n\nFaksova, K. et al. “[COVID-19 Vaccines and Adverse Events of Special Interest: A Multinational Global Vaccine Data Network (GVDN) Cohort Study of 99 Million Vaccinated Individuals](https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0264410X24001270).” Vaccine. 12 Feb 2024.\n\nCOVID Data Tracker. “[COVID-19 Vaccinations in the United States](https:\/\/covid.cdc.gov\/covid-data-tracker\/#vaccinations_vacc-people-booster-percent-pop5).” CDC website. Updated 11 May 2023.\n\nLiu, Angus. “[AstraZeneca withdraws US COVID vaccine application, shifts focus to antibody treatments](https:\/\/www.fiercepharma.com\/pharma\/astrazeneca-withdraws-us-covid-vaccine-application-focus-shifts-antibody-treatments).” Fierce Pharma. 10 Nov 2022.\n\nHviid, Anders. Email with FactCheck.org. 22 Feb 2024.\n\nTheBlaze. “[Blood clots, neurological disorders, and swollen hearts: Multinational study on COVID vaccines paints a damning picture](https:\/\/perma.cc\/J8CM-UD26).” Facebook. 20 Feb 2024.\n\nDr. Anthony G. Jay (@anthonygjay). “[I post a lot of vids but rarely PLUG them WATCH my YouTube vid on this – it’s 6 minutes – before it gets taken down 🤐](https:\/\/perma.cc\/Z54H-ESKX).” Instagram. 20 Feb 2024.\n\nbikinibottom\\_fish 🐟 (@bikinibottom\\_fish). “[Global Study Links COVID-19 Vaccines to Heart and Brain Issues\\!](https:\/\/perma.cc\/V55U-8326)” Instagram. 20 Feb 2024.\n\nPatrioticBabe 🇺🇸 (@babedoesthenews). “[❗️](https:\/\/perma.cc\/B93J-XVC5).” Instagram. 20 Feb 2024.\n\nRASPY RAWLS (@raspy\\_rawls2). “[… We told yall not to take that shyt but hey wat dew we know 🤷🏾‍♂️ …](https:\/\/perma.cc\/ST9S-CCAC) .” Instagram. 20 Feb 2024.\n\nJaimee Michell (@thegaywhostrayed). “[I want to know if you think Trump holds any blame, and if not, why not? COMMENT your thoughts BELOW\\!](https:\/\/perma.cc\/6EX7-CFNP)” Instagram. 20 Feb 2024.\n\nLiberty Counsel (@libertycounsel). “[…](https:\/\/perma.cc\/8QN4-7LVM) [“Based on ‘conservative assumptions,’ the estimated harms of the COVID-19 mRNA vaccines ‘greatly outweigh the rewards,’ the article stated, noting that ‘for every life saved, there were nearly 14 times more deaths caused by the modified mRNA injections.’” …](https:\/\/perma.cc\/8QN4-7LVM)” Instagram. 20 Feb 2024.\n\nShemeka Michelle (@[theshemekamichelle](https:\/\/www.instagram.com\/theshemekamichelle)). “[Remember when they called them “rare” breakthrough cases? Yeah, me too. \\#slight](https:\/\/perma.cc\/D4UM-WH8C).” Instagram. 20 Feb 2024.\n\nMal’aki (@awake.the.mind). “[‘Slight’ will turn to ‘significant’ soon enough. We tried to warn you all but we’re just crazy conspiracy theorists](https:\/\/perma.cc\/MGK4-Y6CV).” Instagram. 20 Feb 2024.\n\nSteinbuch, Yaron. “[COVID vaccines linked to slight increases in heart, brain, blood disorders: study](https:\/\/perma.cc\/2VYG-GB9X).” New York Post. 20 Feb 2024.\n\nVogel, Gretchen and Couzin-Frankel, Jennifer. “[Israel reports link between rare cases of heart inflammation and COVID-19 vaccination in young men](https:\/\/www.science.org\/content\/article\/israel-reports-link-between-rare-cases-heart-inflammation-and-covid-19-vaccination).” Science. 1 Jun 2021.\n\nRobertson, Lori and Kiely, Eugene. “[Q\\&A on the Rare Clotting Events That Caused the J\\&J Pause](https:\/\/www.factcheck.org\/2021\/04\/scicheck-qa-on-the-rare-clotting-events-that-caused-the-jj-pause\/).” FactCheck.org. Updated 6 May 2022.\n\nKahn, Ilana. “[Acute Transverse Myelitis and Acute Disseminated Encephalomyelitis](https:\/\/publications.aap.org\/pediatricsinreview\/article-abstract\/41\/7\/313\/35435\/Acute-Transverse-Myelitis-and-Acute-Disseminated?autologincheck=redirected).” Pediatrics in Review. 1 Jul 2020.\n\nMorgan, Hannah J. et al. “[Acute Disseminated Encephalomyelitis and Transverse Myelitis Following COVID-19 Vaccination – A Self-Controlled Case Series Analysis](https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0264410X24001269).” Vaccine. 12 Feb 2024.\n\n“[Global COVID Vaccine Safety (GCoVS)](https:\/\/globalvaccinedatanetwork.org\/ourwork\/global-covid-vaccine-safety-gcovs).” Global Vaccine Data Network website. Accessed 23 Feb 2024.\n\nMorris, Jeffrey S. Email with FactCheck.org. 22 Feb 2024.\n\nFrontera, Jennifer A. et al. “[Neurological Events Reported after COVID-19 Vaccines: An Analysis of VAERS](https:\/\/pubmed.ncbi.nlm.nih.gov\/35233819\/).” Annals of Neurology. 2 Mar 2022.\n\nMarc Veldhoen (@Marc\\_Veld). “[COVID-19 vaccines and adverse events of special interest: A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals Anything in those anti-vax stories about large scale damage and deaths due to vaccines? No. …](https:\/\/perma.cc\/5JKF-QEKL)” X. 19 Feb 2024.\n\n- Categories\n  - [Debunking Viral Claims](https:\/\/www.factcheck.org\/fake-news\/)\n  - [FactCheck Posts](https:\/\/www.factcheck.org\/the-factcheck-wire\/)\n  - [SciCheck](https:\/\/www.factcheck.org\/scicheck\/)\n- Issue\n  - [coronavirus](https:\/\/www.factcheck.org\/issue\/coronavirus\/)\n  - [COVID-19 vaccination](https:\/\/www.factcheck.org\/issue\/covid-19-vaccination\/)\n  - [myocarditis](https:\/\/www.factcheck.org\/issue\/myocarditis\/)\n  - [vaccination](https:\/\/www.factcheck.org\/issue\/vaccination\/)\n  - [vaccine safety](https:\/\/www.factcheck.org\/issue\/vaccine-safety\/)\n- Misconceptions\n  - [Distortions of Science](https:\/\/www.factcheck.org\/misconceptions\/distortions-of-science\/)\n  - [Vaccination](https:\/\/www.factcheck.org\/misconceptions\/vaccination\/)\n    - [Safety](https:\/\/www.factcheck.org\/misconceptions\/safety\/)\n***\n[Previous StoryPosts Mislead About COVID-19 Vaccine Safety With Out-of-Context Clip of FDA Official](https:\/\/www.factcheck.org\/2024\/02\/posts-mislead-about-covid-19-vaccine-safety-with-out-of-context-clip-of-fda-official\/)\n\n[Next StoryBreaking Down the Immigration Figures](https:\/\/www.factcheck.org\/2024\/02\/breaking-down-the-immigration-figures\/)\n***\n\nAsk FactCheck\n\n**Q: I read this on FB. Is it true? The U.S. Treasury just declared the U.S government is insolvent.**\n\n**A:** **No. That’s the conclusion of an opinion piece that cited a Treasury report showing the government’s liabilities outweigh its assets. But that’s been the case for decades, and unlike an insolvent business, the government can levy taxes.**\n\n[Read the full question and answer](https:\/\/www.factcheck.org\/2026\/04\/the-u-s-treasury-didnt-declare-the-country-insolvent\/)\n\n[View the Ask FactCheck archives](https:\/\/www.factcheck.org\/askfactcheck\/)\n\nHave a question? [Ask us.](https:\/\/www.factcheck.org\/ask-factcheck\/ask-us-a-question\/)\n\n[Donate Now Because facts matter.](https:\/\/giving.aws.cloud.upenn.edu\/?fastStart=simpleForm&program=ANS&fund=602014 \"Because facts matter.\")\n\n[![SciCheck's COVID-19\/Vaccination Project](https:\/\/cdn.factcheck.org\/UploadedFiles\/misconceptions2.png) SciCheck's COVID-19\/Vaccination Project Preempting and exposing vaccination and COVID-19 misinformation.](https:\/\/www.factcheck.org\/covid-misconceptions\/)\n\n[![Proyecto de Vacunación\/COVID-19](https:\/\/cdn.factcheck.org\/UploadedFiles\/misconceptions2.png) Proyecto de Vacunación\/COVID-19 Precaviendo y exponiendo la desinformación sobre el COVID-19 y sus vacunas](https:\/\/www.factcheck.org\/es\/covid-misconceptions\/)\n\n[![SciCheck](https:\/\/cdn.factcheck.org\/UploadedFiles\/fc-icon-scicheck.png) SciCheck Fact-checking science-based claims.](https:\/\/www.factcheck.org\/scicheck\/)\n\n[![Viral Spiral](https:\/\/cdn.factcheck.org\/UploadedFiles\/fc-icon-viralspiral.png) Viral Spiral Don’t get spun by internet rumors.](https:\/\/www.factcheck.org\/hot-topics\/)\n\n[![Newsletter](https:\/\/cdn.factcheck.org\/UploadedFiles\/fc-icon-signup.png) Newsletter Get our free weekly email.](https:\/\/www.factcheck.org\/subscribe)\n\n[![Mailbag](https:\/\/cdn.factcheck.org\/UploadedFiles\/fc-icon-mailbag.png) Mailbag Letters from our readers.](https:\/\/www.factcheck.org\/factcheck-mailbag\/)\n\n[![On the Air](https:\/\/cdn.factcheck.org\/UploadedFiles\/fc-icon-ota.png) On the Air Our staff on TV and radio.](https:\/\/www.factcheck.org\/on-the-air)\n\n[![NewsFeed Defenders](https:\/\/cdn.factcheck.org\/UploadedFiles\/factchecksidebar_icon-1.png) NewsFeed Defenders A media literacy game to detect misinformation.](https:\/\/www.factcheck.org\/newsfeed-defenders\/)\n\n- [Archives](https:\/\/www.factcheck.org\/archives\/)\n- [Privacy](https:\/\/www.factcheck.org\/privacy\/)\n- [Copyright Policy](https:\/\/www.factcheck.org\/copyright-policy\/)\n- [Contact Us](https:\/\/www.factcheck.org\/about\/contact-us\/)\n- [Report Accessibility Issues and Get Help](https:\/\/accessibility.web-resources.upenn.edu\/get-help)\n\n© Copyright 2026 FactCheck.org ®  \nA Project of The Annenberg Public Policy Center of the University of Pennsylvania","attrs_readable_markdown":"## SciCheck Digest\nAn international study of around 99 million people confirmed known serious side effects of COVID-19 vaccination. It also identified a possible relationship between the first dose of the Moderna vaccine and a small risk of a neurological condition. Social media posts about the study left out information on the vaccines’ benefits and the rarity of the side effects.\n***\n## Full Story\nCOVID-19 vaccines — like all [vaccines](https:\/\/www.factcheck.org\/scicheck_digest\/how-do-we-know-vaccines-are-safe\/) and other medical products — come with side effects, including [serious side effects](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/adverse-events.html) in rare cases. The vaccines were rolled out to protect people from a novel virus that has [killed](https:\/\/www.factcheck.org\/2024\/01\/scicheck-tucker-carlson-video-spreads-falsehoods-on-covid-19-vaccines-who-accord\/) millions of people globally and would likely have killed millions more without the arrival of the vaccines. There is a broad consensus from [experts](https:\/\/www.who.int\/news-room\/questions-and-answers\/item\/coronavirus-disease-\\(covid-19\\)-vaccines) and [governmental](https:\/\/www.fda.gov\/news-events\/press-announcements\/fda-takes-action-updated-mrna-covid-19-vaccines-better-protect-against-currently-circulating) health [agencies](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/safety-of-vaccines.html) that the benefits of COVID-19 vaccination outweigh the risks.\n\nResearchers have [scrutinized](https:\/\/www.factcheck.org\/scicheck_digest\/how-safe-are-the-vaccines\/) the COVID-19 vaccines’ safety and continue to do so. A [study](https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0264410X24001270) published Feb. 12 in the journal Vaccine reported on an international group of more than 99 million people who received COVID-19 vaccines, primarily finding links to known rare side effects. The study largely focused on the Pfizer\/BioNTech and Moderna vaccines, which have been [widely given](https:\/\/covid.cdc.gov\/covid-data-tracker\/#vaccinations_vacc-people-booster-percent-pop5) in the U.S., as well as the AstraZeneca vaccine, which was [never authorized](https:\/\/www.fiercepharma.com\/pharma\/astrazeneca-withdraws-us-covid-vaccine-application-focus-shifts-antibody-treatments) in the U.S.\n\n![](https:\/\/cdn.factcheck.org\/UploadedFiles\/SciCHECKsquare_4-161x145.png)\n\n“What we take away, is that the Covid-19 vaccination campaigns have been very effective in preventing severe disease,” study co-author [Anders Hviid](https:\/\/en.ssi.dk\/about-us\/contact\/employees\/a\/anders-peter-hviid-aii), head of the department of epidemiology research at the Statens Serum Institut in Denmark, told us in an email. “The few serious side effects that we have observed in this and other studies have been rare.”\n\nMany popular posts on social media have shared results from the study, some lacking the context that the identified [health problems](https:\/\/perma.cc\/J8CM-UD26) are [rare](https:\/\/perma.cc\/Z54H-ESKX), that [most](https:\/\/perma.cc\/V55U-8326) aren’t [new](https:\/\/perma.cc\/B93J-XVC5) and that the vaccines have proven benefits. Various posts made unfounded claims, stating or implying that people [should not](https:\/\/perma.cc\/ST9S-CCAC) have [received](https:\/\/perma.cc\/6EX7-CFNP) the [vaccines](https:\/\/perma.cc\/7TKY-2YH7), that the risks [outweigh](https:\/\/perma.cc\/8QN4-7LVM) the benefits or that the [risk](https:\/\/perma.cc\/D4UM-WH8C) of the rare side effects is [greater](https:\/\/perma.cc\/MGK4-Y6CV) than was reported in the study.\n\n“Hundreds of millions of people were used as lab rats and now the truth that WE ALL ALREADY KNEW can no longer be denied,” said one popular [post](https:\/\/perma.cc\/6EX7-CFNP), referring to the vaccines as “experimental” and “UNTESTED.” The post shared a screenshot of the headline of a New York Post [article](https:\/\/perma.cc\/2VYG-GB9X) about the new study, which read, “COVID vaccines linked to slight increases in heart, brain, blood disorders: study.”\n\n“This thing was forced on people who faced almost no risk from Covid,” said another widely read [post](https:\/\/perma.cc\/4SP3-55WN). “It is completely unacceptable.” The post shared statistics from the paper without making it clear that serious health problems after vaccination were rare and that risk varied by vaccine type and dose.\n\nThe Vaccine study confirmed that the Moderna and Pfizer\/BioNTech vaccines are linked in rare cases to myocarditis and pericarditis, conditions [involving](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/adverse-events.html) inflammation of the heart muscle and lining. The rate of myocarditis was most elevated after the second dose of the Moderna vaccine. Myocarditis risk — which is greatest in men in their late teens and early twenties — was [identified](https:\/\/www.science.org\/content\/article\/israel-reports-link-between-rare-cases-heart-inflammation-and-covid-19-vaccination) via vaccine safety monitoring and first reported in 2021. Based on the current evidence, the [CDC](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/adverse-events.html) says, the benefit of vaccination outweighs the risk of these conditions, which improve for most people after medical treatment and rest.\n\nThe study confirmed neurological and blood clotting conditions associated with the AstraZeneca vaccine. In the U.S., these [problems](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/adverse-events.html) were [linked](https:\/\/www.factcheck.org\/2021\/04\/scicheck-qa-on-the-rare-clotting-events-that-caused-the-jj-pause\/) to the Johnson & Johnson vaccine, contributing to this vaccine no longer being recommended or available.\n\nThe study also identified a new possible safety signal indicating a potential link between the first dose of the Moderna and AstraZeneca vaccines and rare neurological conditions. This included an association between the first doses of the vaccines and acute disseminated encephalomyelitis, or ADEM, an autoimmune [condition](https:\/\/publications.aap.org\/pediatricsinreview\/article-abstract\/41\/7\/313\/35435\/Acute-Transverse-Myelitis-and-Acute-Disseminated) that [causes](https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0264410X24001269) inflammation of the brain and spinal cord.\n\nHviid emphasized that the researchers only saw these neurological events after first doses of the two vaccines. “We did not see these signals following further doses of these two Covid-19 vaccines, nor did we see them after any dose of the Pfizer\/BioNTech vaccine which has been more widely used,” he said.\n\n“We are also talking about very rare events,” Hviid continued. “As an example, the association between the first dose of Moderna and acute inflammation of the brain and spine would, if causal, correspond to 1 case per 1.75 million vaccinated. It is only due to the sheer scale of our study, that we have been able to identify this minute potential risk.”\n\n## Study Bolsters the Evidence Serious COVID-19 Vaccine Side Effects Are Rare\nThe Vaccine [study](https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0264410X24001270#s0095) drew on national or regional health records from eight countries with institutions participating in the [Global Vaccine Data Network](https:\/\/globalvaccinedatanetwork.org\/ourwork\/global-covid-vaccine-safety-gcovs), an international group that studies vaccine safety. The researchers analyzed health outcomes after around 184 million doses of the Pfizer\/BioNTech vaccine, 36 million doses of the Moderna vaccine and 23 million doses of the AstraZeneca vaccine.\n\nThe researchers focused on 13 health problems that either had a known association with vaccination or for which there was some rationale to investigate whether there was an association. To determine whether the health problems were associated with vaccination, they compared the expected rates of the health problems — or the number of health events that should occur based on background rates in the regions studied — with the number of events they observed in the 42 days after vaccination.\n\n“This study confirms the primary already detected and validated side effects established by previous literature,” [Jeffrey S. Morris](https:\/\/www.dbei.med.upenn.edu\/bio\/jeffrey-s-morris-phd), director of the division of biostatistics at the University of Pennsylvania’s Perelman School of Medicine, told us via email, referring to the rare heart conditions associated with the Moderna and Pfizer\/BioNTech vaccines, as well as the rare conditions associated with the AstraZeneca and Johnson & Johnson vaccines.\n\nMorris said that findings on ADEM — the rare autoimmune neurological condition linked to first doses of the Moderna and AstraZeneca vaccines — “might be a new safety signal.”\n\nADEM [involves](https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0264410X24001269) inflammation to the brain and spinal cord, arising most often in children following an infectious illness. It has a [sudden onset](https:\/\/publications.aap.org\/pediatricsinreview\/article-abstract\/41\/7\/313\/35435\/Acute-Transverse-Myelitis-and-Acute-Disseminated) and typically eventually improves, with a full recovery in many, although not all, cases.\n\nAfter the first dose of the Moderna vaccine, researchers observed seven ADEM cases, when they expected two. As we’ve said, Hviid calculated the rate of this side effect — if ultimately shown to be related to vaccination — to be 1 in 1.75 million following the first dose of the Moderna vaccine.\n\nThe data show “this was indeed an EXTREMELY rare adverse event,” Morris said, referring to ADEM. “It is understandable at this incidence rate why it may not have been detected before now, and why a study with 99 million participants like this is important to find even the most rare serious adverse events that are potential minority harm risks of these vaccines.”\n\nThe authors of the study wrote that more research is needed into ADEM following COVID-19 vaccination, saying that “the number of cases of this rare event were small and the confidence interval wide, so results should be interpreted with caution and confirmed in future studies.” The authors also wrote that neurological [events](https:\/\/pubmed.ncbi.nlm.nih.gov\/35233819\/) have been found to occur at a much higher rate after COVID-19 than after COVID-19 vaccination.\n\nThe study means that “early warning systems are solid,” said [Marc Veldhoen](https:\/\/imm.medicina.ulisboa.pt\/investigation\/laboratories\/marc-veldhoen-lab\/#intro), an immunologist at the Instituto de Medicina Molecular João Lobo Antunes in Portugal, in a [post](https:\/\/perma.cc\/5JKF-QEKL) on X, formerly known as Twitter. “To avoid any adverse reaction is not possible, but, identifying those at higher risk may be possible.”\n\nIdentifying those at greater risk of side effects can help guide decisions on which vaccines to recommend and what problems doctors should watch for in their patients.\n***\n*Editor’s note: SciCheck’s articles providing accurate health information and correcting health misinformation are made possible by a grant from the Robert Wood Johnson Foundation. The foundation has [no control](https:\/\/www.factcheck.org\/2021\/04\/scicheck-and-our-committment-to-transparency\/) over FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation.*\n\n## Sources\n“[How do we know vaccines are safe?](https:\/\/www.factcheck.org\/scicheck_digest\/how-do-we-know-vaccines-are-safe\/)” FactCheck.org. Updated 8 Jul 2021.\n\n“[Selected Adverse Events Reported after COVID-19 Vaccination](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/adverse-events.html).” CDC website. Updated 12 Sep 2023.\n\nYandell, Kate. “[Tucker Carlson Video Spreads Falsehoods on COVID-19 Vaccines, WHO Accord](https:\/\/www.factcheck.org\/2024\/01\/scicheck-tucker-carlson-video-spreads-falsehoods-on-covid-19-vaccines-who-accord\/).” FactCheck.org. 13 Jan 2024.\n\n“[Safety of COVID-19 Vaccines](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/safety\/safety-of-vaccines.html).” CDC website. 3 Nov 2023.\n\n“[How safe are the COVID-19 vaccines?](https:\/\/www.factcheck.org\/scicheck_digest\/how-safe-are-the-vaccines\/)” FactCheck.org. Updated 17 May 2022.\n\nFaksova, K. et al. “[COVID-19 Vaccines and Adverse Events of Special Interest: A Multinational Global Vaccine Data Network (GVDN) Cohort Study of 99 Million Vaccinated Individuals](https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0264410X24001270).” Vaccine. 12 Feb 2024.\n\nCOVID Data Tracker. “[COVID-19 Vaccinations in the United States](https:\/\/covid.cdc.gov\/covid-data-tracker\/#vaccinations_vacc-people-booster-percent-pop5).” CDC website. Updated 11 May 2023.\n\nLiu, Angus. “[AstraZeneca withdraws US COVID vaccine application, shifts focus to antibody treatments](https:\/\/www.fiercepharma.com\/pharma\/astrazeneca-withdraws-us-covid-vaccine-application-focus-shifts-antibody-treatments).” Fierce Pharma. 10 Nov 2022.\n\nHviid, Anders. Email with FactCheck.org. 22 Feb 2024.\n\nTheBlaze. “[Blood clots, neurological disorders, and swollen hearts: Multinational study on COVID vaccines paints a damning picture](https:\/\/perma.cc\/J8CM-UD26).” Facebook. 20 Feb 2024.\n\nDr. Anthony G. Jay (@anthonygjay). “[I post a lot of vids but rarely PLUG them WATCH my YouTube vid on this – it’s 6 minutes – before it gets taken down 🤐](https:\/\/perma.cc\/Z54H-ESKX).” Instagram. 20 Feb 2024.\n\nbikinibottom\\_fish 🐟 (@bikinibottom\\_fish). “[Global Study Links COVID-19 Vaccines to Heart and Brain Issues\\!](https:\/\/perma.cc\/V55U-8326)” Instagram. 20 Feb 2024.\n\nPatrioticBabe 🇺🇸 (@babedoesthenews). “[❗️](https:\/\/perma.cc\/B93J-XVC5).” Instagram. 20 Feb 2024.\n\nRASPY RAWLS (@raspy\\_rawls2). “[… We told yall not to take that shyt but hey wat dew we know 🤷🏾‍♂️ …](https:\/\/perma.cc\/ST9S-CCAC) .” Instagram. 20 Feb 2024.\n\nJaimee Michell (@thegaywhostrayed). “[I want to know if you think Trump holds any blame, and if not, why not? COMMENT your thoughts BELOW\\!](https:\/\/perma.cc\/6EX7-CFNP)” Instagram. 20 Feb 2024.\n\nLiberty Counsel (@libertycounsel). “[…](https:\/\/perma.cc\/8QN4-7LVM) [“Based on ‘conservative assumptions,’ the estimated harms of the COVID-19 mRNA vaccines ‘greatly outweigh the rewards,’ the article stated, noting that ‘for every life saved, there were nearly 14 times more deaths caused by the modified mRNA injections.’” …](https:\/\/perma.cc\/8QN4-7LVM)” Instagram. 20 Feb 2024.\n\nShemeka Michelle (@[theshemekamichelle](https:\/\/www.instagram.com\/theshemekamichelle)). “[Remember when they called them “rare” breakthrough cases? Yeah, me too. \\#slight](https:\/\/perma.cc\/D4UM-WH8C).” Instagram. 20 Feb 2024.\n\nMal’aki (@awake.the.mind). “[‘Slight’ will turn to ‘significant’ soon enough. We tried to warn you all but we’re just crazy conspiracy theorists](https:\/\/perma.cc\/MGK4-Y6CV).” Instagram. 20 Feb 2024.\n\nSteinbuch, Yaron. “[COVID vaccines linked to slight increases in heart, brain, blood disorders: study](https:\/\/perma.cc\/2VYG-GB9X).” New York Post. 20 Feb 2024.\n\nVogel, Gretchen and Couzin-Frankel, Jennifer. “[Israel reports link between rare cases of heart inflammation and COVID-19 vaccination in young men](https:\/\/www.science.org\/content\/article\/israel-reports-link-between-rare-cases-heart-inflammation-and-covid-19-vaccination).” Science. 1 Jun 2021.\n\nRobertson, Lori and Kiely, Eugene. “[Q\\&A on the Rare Clotting Events That Caused the J\\&J Pause](https:\/\/www.factcheck.org\/2021\/04\/scicheck-qa-on-the-rare-clotting-events-that-caused-the-jj-pause\/).” FactCheck.org. Updated 6 May 2022.\n\nKahn, Ilana. “[Acute Transverse Myelitis and Acute Disseminated Encephalomyelitis](https:\/\/publications.aap.org\/pediatricsinreview\/article-abstract\/41\/7\/313\/35435\/Acute-Transverse-Myelitis-and-Acute-Disseminated?autologincheck=redirected).” Pediatrics in Review. 1 Jul 2020.\n\nMorgan, Hannah J. et al. “[Acute Disseminated Encephalomyelitis and Transverse Myelitis Following COVID-19 Vaccination – A Self-Controlled Case Series Analysis](https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0264410X24001269).” Vaccine. 12 Feb 2024.\n\n“[Global COVID Vaccine Safety (GCoVS)](https:\/\/globalvaccinedatanetwork.org\/ourwork\/global-covid-vaccine-safety-gcovs).” Global Vaccine Data Network website. Accessed 23 Feb 2024.\n\nMorris, Jeffrey S. Email with FactCheck.org. 22 Feb 2024.\n\nFrontera, Jennifer A. et al. “[Neurological Events Reported after COVID-19 Vaccines: An Analysis of VAERS](https:\/\/pubmed.ncbi.nlm.nih.gov\/35233819\/).” Annals of Neurology. 2 Mar 2022.\n\nMarc Veldhoen (@Marc\\_Veld). “[COVID-19 vaccines and adverse events of special interest: A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals Anything in those anti-vax stories about large scale damage and deaths due to vaccines? No. …](https:\/\/perma.cc\/5JKF-QEKL)” X. 19 Feb 2024.","meta_canonical":null}

3. Robots.txt Check

Query:

Response:

4. Spam/Ban Check

Query:

Response:

5. Seen Status Check

ℹ️ Skipped - page is already crawled

📄

INDEXABLE

✅

CRAWLED

5 hours ago

🤖

ROBOTS ALLOWED

Page Info Filters

Filter	Status	Condition	Details
HTTP status	PASS	`download_http_code = 200`	HTTP 200
Age cutoff	PASS	`download_stamp > now() - 6 MONTH`	0 months ago
History drop	PASS	`isNull(history_drop_reason)`	No drop reason
Spam/ban	PASS	`fh_dont_index != 1 AND ml_spam_score = 0`	ml_spam_score=0
Canonical	PASS	`meta_canonical IS NULL OR = '' OR = src_unparsed`	Not set

Page Details

Property	Value
URL	https://www.factcheck.org/2024/02/study-largely-confirms-known-rare-covid-19-vaccine-side-effects/
Last Crawled	2026-04-16 02:03:20 (5 hours ago)
First Indexed	2024-02-27 22:06:41 (2 years ago)
HTTP Status Code	200
Meta Title	Study Largely Confirms Known, Rare COVID-19 Vaccine Side Effects - FactCheck.org
Meta Description	null
Meta Canonical	null
Boilerpipe Text	SciCheck Digest An international study of around 99 million people confirmed known serious side effects of COVID-19 vaccination. It also identified a possible relationship between the first dose of the Moderna vaccine and a small risk of a neurological condition. Social media posts about the study left out information on the vaccines’ benefits and the rarity of the side effects. Full Story COVID-19 vaccines — like all vaccines and other medical products — come with side effects, including serious side effects in rare cases. The vaccines were rolled out to protect people from a novel virus that has killed millions of people globally and would likely have killed millions more without the arrival of the vaccines. There is a broad consensus from experts and governmental health agencies that the benefits of COVID-19 vaccination outweigh the risks. Researchers have scrutinized the COVID-19 vaccines’ safety and continue to do so. A study published Feb. 12 in the journal Vaccine reported on an international group of more than 99 million people who received COVID-19 vaccines, primarily finding links to known rare side effects. The study largely focused on the Pfizer/BioNTech and Moderna vaccines, which have been widely given in the U.S., as well as the AstraZeneca vaccine, which was never authorized in the U.S. “What we take away, is that the Covid-19 vaccination campaigns have been very effective in preventing severe disease,” study co-author Anders Hviid , head of the department of epidemiology research at the Statens Serum Institut in Denmark, told us in an email. “The few serious side effects that we have observed in this and other studies have been rare.” Many popular posts on social media have shared results from the study, some lacking the context that the identified health problems are rare , that most aren’t new and that the vaccines have proven benefits. Various posts made unfounded claims, stating or implying that people should not have received the vaccines , that the risks outweigh the benefits or that the risk of the rare side effects is greater than was reported in the study. “Hundreds of millions of people were used as lab rats and now the truth that WE ALL ALREADY KNEW can no longer be denied,” said one popular post , referring to the vaccines as “experimental” and “UNTESTED.” The post shared a screenshot of the headline of a New York Post article about the new study, which read, “COVID vaccines linked to slight increases in heart, brain, blood disorders: study.” “This thing was forced on people who faced almost no risk from Covid,” said another widely read post . “It is completely unacceptable.” The post shared statistics from the paper without making it clear that serious health problems after vaccination were rare and that risk varied by vaccine type and dose. The Vaccine study confirmed that the Moderna and Pfizer/BioNTech vaccines are linked in rare cases to myocarditis and pericarditis, conditions involving inflammation of the heart muscle and lining. The rate of myocarditis was most elevated after the second dose of the Moderna vaccine. Myocarditis risk — which is greatest in men in their late teens and early twenties — was identified via vaccine safety monitoring and first reported in 2021. Based on the current evidence, the CDC says, the benefit of vaccination outweighs the risk of these conditions, which improve for most people after medical treatment and rest. The study confirmed neurological and blood clotting conditions associated with the AstraZeneca vaccine. In the U.S., these problems were linked to the Johnson & Johnson vaccine, contributing to this vaccine no longer being recommended or available. The study also identified a new possible safety signal indicating a potential link between the first dose of the Moderna and AstraZeneca vaccines and rare neurological conditions. This included an association between the first doses of the vaccines and acute disseminated encephalomyelitis, or ADEM, an autoimmune condition that causes inflammation of the brain and spinal cord. Hviid emphasized that the researchers only saw these neurological events after first doses of the two vaccines. “We did not see these signals following further doses of these two Covid-19 vaccines, nor did we see them after any dose of the Pfizer/BioNTech vaccine which has been more widely used,” he said. “We are also talking about very rare events,” Hviid continued. “As an example, the association between the first dose of Moderna and acute inflammation of the brain and spine would, if causal, correspond to 1 case per 1.75 million vaccinated. It is only due to the sheer scale of our study, that we have been able to identify this minute potential risk.” Study Bolsters the Evidence Serious COVID-19 Vaccine Side Effects Are Rare The Vaccine study drew on national or regional health records from eight countries with institutions participating in the Global Vaccine Data Network , an international group that studies vaccine safety. The researchers analyzed health outcomes after around 184 million doses of the Pfizer/BioNTech vaccine, 36 million doses of the Moderna vaccine and 23 million doses of the AstraZeneca vaccine. The researchers focused on 13 health problems that either had a known association with vaccination or for which there was some rationale to investigate whether there was an association. To determine whether the health problems were associated with vaccination, they compared the expected rates of the health problems — or the number of health events that should occur based on background rates in the regions studied — with the number of events they observed in the 42 days after vaccination. “This study confirms the primary already detected and validated side effects established by previous literature,” Jeffrey S. Morris , director of the division of biostatistics at the University of Pennsylvania’s Perelman School of Medicine, told us via email, referring to the rare heart conditions associated with the Moderna and Pfizer/BioNTech vaccines, as well as the rare conditions associated with the AstraZeneca and Johnson & Johnson vaccines. Morris said that findings on ADEM — the rare autoimmune neurological condition linked to first doses of the Moderna and AstraZeneca vaccines — “might be a new safety signal.” ADEM involves inflammation to the brain and spinal cord, arising most often in children following an infectious illness. It has a sudden onset and typically eventually improves, with a full recovery in many, although not all, cases. After the first dose of the Moderna vaccine, researchers observed seven ADEM cases, when they expected two. As we’ve said, Hviid calculated the rate of this side effect — if ultimately shown to be related to vaccination — to be 1 in 1.75 million following the first dose of the Moderna vaccine. The data show “this was indeed an EXTREMELY rare adverse event,” Morris said, referring to ADEM. “It is understandable at this incidence rate why it may not have been detected before now, and why a study with 99 million participants like this is important to find even the most rare serious adverse events that are potential minority harm risks of these vaccines.” The authors of the study wrote that more research is needed into ADEM following COVID-19 vaccination, saying that “the number of cases of this rare event were small and the confidence interval wide, so results should be interpreted with caution and confirmed in future studies.” The authors also wrote that neurological events have been found to occur at a much higher rate after COVID-19 than after COVID-19 vaccination. The study means that “early warning systems are solid,” said Marc Veldhoen , an immunologist at the Instituto de Medicina Molecular João Lobo Antunes in Portugal, in a post on X, formerly known as Twitter. “To avoid any adverse reaction is not possible, but, identifying those at higher risk may be possible.” Identifying those at greater risk of side effects can help guide decisions on which vaccines to recommend and what problems doctors should watch for in their patients. Editor’s note: SciCheck’s articles providing accurate health information and correcting health misinformation are made possible by a grant from the Robert Wood Johnson Foundation. The foundation has no control over FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation. Sources “ How do we know vaccines are safe? ” FactCheck.org. Updated 8 Jul 2021. “ Selected Adverse Events Reported after COVID-19 Vaccination .” CDC website. Updated 12 Sep 2023. Yandell, Kate. “ Tucker Carlson Video Spreads Falsehoods on COVID-19 Vaccines, WHO Accord .” FactCheck.org. 13 Jan 2024. “ Safety of COVID-19 Vaccines .” CDC website. 3 Nov 2023. “ How safe are the COVID-19 vaccines? ” FactCheck.org. Updated 17 May 2022. Faksova, K. et al. “ COVID-19 Vaccines and Adverse Events of Special Interest: A Multinational Global Vaccine Data Network (GVDN) Cohort Study of 99 Million Vaccinated Individuals .” Vaccine. 12 Feb 2024. COVID Data Tracker. “ COVID-19 Vaccinations in the United States .” CDC website. Updated 11 May 2023. Liu, Angus. “ AstraZeneca withdraws US COVID vaccine application, shifts focus to antibody treatments .” Fierce Pharma. 10 Nov 2022. Hviid, Anders. Email with FactCheck.org. 22 Feb 2024. TheBlaze. “ Blood clots, neurological disorders, and swollen hearts: Multinational study on COVID vaccines paints a damning picture .” Facebook. 20 Feb 2024. Dr. Anthony G. Jay (@anthonygjay). “ I post a lot of vids but rarely PLUG them WATCH my YouTube vid on this – it’s 6 minutes – before it gets taken down 🤐 .” Instagram. 20 Feb 2024. bikinibottom_fish 🐟 (@bikinibottom_fish). “ Global Study Links COVID-19 Vaccines to Heart and Brain Issues! ” Instagram. 20 Feb 2024. PatrioticBabe 🇺🇸 (@babedoesthenews). “ ❗️ .” Instagram. 20 Feb 2024. RASPY RAWLS (@raspy_rawls2). “ … We told yall not to take that shyt but hey wat dew we know 🤷🏾‍♂️ … .” Instagram. 20 Feb 2024. Jaimee Michell (@thegaywhostrayed). “ I want to know if you think Trump holds any blame, and if not, why not? COMMENT your thoughts BELOW! ” Instagram. 20 Feb 2024. Liberty Counsel (@libertycounsel). “ … “Based on ‘conservative assumptions,’ the estimated harms of the COVID-19 mRNA vaccines ‘greatly outweigh the rewards,’ the article stated, noting that ‘for every life saved, there were nearly 14 times more deaths caused by the modified mRNA injections.’” … ” Instagram. 20 Feb 2024. Shemeka Michelle (@ theshemekamichelle ). “ Remember when they called them “rare” breakthrough cases? Yeah, me too. #slight .” Instagram. 20 Feb 2024. Mal’aki (@awake.the.mind). “ ‘Slight’ will turn to ‘significant’ soon enough. We tried to warn you all but we’re just crazy conspiracy theorists .” Instagram. 20 Feb 2024. Steinbuch, Yaron. “ COVID vaccines linked to slight increases in heart, brain, blood disorders: study .” New York Post. 20 Feb 2024. Vogel, Gretchen and Couzin-Frankel, Jennifer. “ Israel reports link between rare cases of heart inflammation and COVID-19 vaccination in young men .” Science. 1 Jun 2021. Robertson, Lori and Kiely, Eugene. “ Q&A on the Rare Clotting Events That Caused the J&J Pause .” FactCheck.org. Updated 6 May 2022. Kahn, Ilana. “ Acute Transverse Myelitis and Acute Disseminated Encephalomyelitis .” Pediatrics in Review. 1 Jul 2020. Morgan, Hannah J. et al. “ Acute Disseminated Encephalomyelitis and Transverse Myelitis Following COVID-19 Vaccination – A Self-Controlled Case Series Analysis .” Vaccine. 12 Feb 2024. “ Global COVID Vaccine Safety (GCoVS) .” Global Vaccine Data Network website. Accessed 23 Feb 2024. Morris, Jeffrey S. Email with FactCheck.org. 22 Feb 2024. Frontera, Jennifer A. et al. “ Neurological Events Reported after COVID-19 Vaccines: An Analysis of VAERS .” Annals of Neurology. 2 Mar 2022. Marc Veldhoen (@Marc_Veld). “ COVID-19 vaccines and adverse events of special interest: A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals Anything in those anti-vax stories about large scale damage and deaths due to vaccines? No. … ” X. 19 Feb 2024.
Markdown	[Skip to main content](https://www.factcheck.org/2024/02/study-largely-confirms-known-rare-covid-19-vaccine-side-effects/#main) [FactCheck.org®](https://www.factcheck.org/) A Project of The Annenberg Public Policy Center [![Become a Facebook fan](https://cdn.factcheck.org/UploadedFiles/fc-icon-facebook-mini.png)](https://www.facebook.com/factcheck.org) [![Follow us on Twitter](https://cdn.factcheck.org/UploadedFiles/x-icon-logo-black.png)](https://www.x.com/factcheckdotorg) [![Get the RSS feed](https://cdn.factcheck.org/UploadedFiles/fc-icon-rss.png)](https://www.factcheck.org/feed/) [![Follow on Insta](https://cdn.factcheck.org/UploadedFiles/fc-icon-instagram-1.png)](https://www.instagram.com/factcheckorg/) [![Sign up for the email newsletter](https://cdn.factcheck.org/UploadedFiles/fc-icon-email.png)](https://www.factcheck.org/subscribe/) [![Help us hold politicians accountable. ](https://cdn.factcheck.org/UploadedFiles/fc-icon-donate.png)](https://giving.aws.cloud.upenn.edu/?fastStart=simpleForm&program=ANS&fund=602014) SciCheck’s COVID-19/Vaccination Project [Learn More](https://www.factcheck.org/covid-misconceptions) [FactCheck.org®](https://www.factcheck.org/) - [Home](https://www.factcheck.org/ "Home") - [Articles](https://www.factcheck.org/2024/02/study-largely-confirms-known-rare-covid-19-vaccine-side-effects/ "Articles") - [FactCheck Posts](https://www.factcheck.org/the-factcheck-wire/ "FactCheck Posts") - [SciCheck](https://www.factcheck.org/scicheck/ "SciCheck") - [En Español](https://www.factcheck.org/es/en-espanol/ "En Español") - [Project 2025 series](https://www.factcheck.org/issue/project-2025-series/ "Project 2025 series") - [Debunking Viral Claims](https://www.factcheck.org/fake-news/ "Debunking Viral Claims") - [Ask a Question](https://www.factcheck.org/2024/02/study-largely-confirms-known-rare-covid-19-vaccine-side-effects/ "Ask a Question") - [Ask FactCheck](https://www.factcheck.org/askfactcheck/ "Ask FactCheck") - [Ask SciCheck](https://www.factcheck.org/askscicheck/ "Ask SciCheck") - [Donate](https://giving.aws.cloud.upenn.edu/fund?fastStart=simpleForm&program=ANS&fund=602014 "Donate") - [Topics](https://www.factcheck.org/2024/02/study-largely-confirms-known-rare-covid-19-vaccine-side-effects/ "Topics") - [President Trump](https://www.factcheck.org/person/donald-trump/ "President Trump") - [Robert F. Kennedy Jr.](https://www.factcheck.org/person/robert-f-kennedy-jr/ "Robert F. Kennedy Jr.") - [immigration](https://www.factcheck.org/issue/immigration/ "immigration") - [climate change](https://www.factcheck.org/issue/climate-change/ "climate change") - [coronavirus](https://www.factcheck.org/issue/coronavirus/ "coronavirus") - [tariffs](https://www.factcheck.org/issue/tariffs/ "tariffs") - [View All](https://www.factcheck.org/archives/ "View All") - [About Us](https://www.factcheck.org/2024/02/study-largely-confirms-known-rare-covid-19-vaccine-side-effects/ "About Us") - [Our Mission](https://www.factcheck.org/about/our-mission/ "Our Mission") - [Our Process](https://www.factcheck.org/our-process/ "Our Process") - [Our Funding](https://www.factcheck.org/our-funding/ "Our Funding") - [Our Staff](https://www.factcheck.org/our-staff/ "Our Staff") - [Undergraduate Fellows](https://www.factcheck.org/undergraduate-fellows/ "Undergraduate Fellows") - [Awards](https://www.factcheck.org/awards/ "Awards") - [Request a Correction](https://www.factcheck.org/request-a-correction/ "Request a Correction") - [Contact Us](https://www.factcheck.org/about/contact-us/ "Contact Us") - [Search](https://www.factcheck.org/search/ "Search") - [More](https://www.factcheck.org/2024/02/study-largely-confirms-known-rare-covid-19-vaccine-side-effects/ "More") - [Viral Claims](https://www.factcheck.org/hot-topics/ "Viral Claims") - [Newsletter](https://www.factcheck.org/subscribe/ "Newsletter") - [Instagram](https://www.instagram.com/factcheckorg/ "Instagram") - [Threads](https://www.threads.net/@factcheckorg "Threads") - [YouTube](https://www.youtube.com/factcheckdotorg "YouTube") - [TikTok](https://www.tiktok.com/@factcheckorg "TikTok") - [Facebook](https://www.facebook.com/factcheck.org "Facebook") - [X](https://twitter.com/factcheckdotorg "X") - [FactCheck On the Air](https://www.factcheck.org/on-the-air/ "FactCheck On the Air") [Debunking Viral Claims](https://www.factcheck.org/fake-news/) › [FactCheck Posts](https://www.factcheck.org/the-factcheck-wire/) › [SciCheck](https://www.factcheck.org/scicheck/) # Study Largely Confirms Known, Rare COVID-19 Vaccine Side Effects By [Kate Yandell](https://www.factcheck.org/author/kate-yandell/ "Posts by Kate Yandell") Posted on February 27, 2024 * This article is available in both English and Español ## SciCheck Digest An international study of around 99 million people confirmed known serious side effects of COVID-19 vaccination. It also identified a possible relationship between the first dose of the Moderna vaccine and a small risk of a neurological condition. Social media posts about the study left out information on the vaccines’ benefits and the rarity of the side effects. ![](https://cdn.factcheck.org/UploadedFiles/rwjf-icon-vaccination-04%402x.png) How safe are the COVID-19 vaccines? [How safe are the COVID-19 vaccines?](https://www.factcheck.org/scicheck_digest/how-safe-are-the-vaccines/) More than [half a billion](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/safety-of-vaccines.html) doses of COVID-19 vaccines have now been administered in the U.S. and only a few, very rare, safety concerns have emerged. The vast majority of people experience only minor, temporary side effects such as pain at the injection site, fatigue, headache, or muscle pain — or no side effects at all. As the Centers for Disease Control and Prevention has [said](https://archive.md/fG255), these vaccines “have undergone and will continue to undergo the most intensive safety monitoring in U.S. history.” A small number of severe allergic reactions known as anaphylaxis, which are expected with any vaccine, [have](https://www.cdc.gov/mmwr/volumes/70/wr/mm7004e1.htm?s_cid=mm7004e1_w) [occurred](https://www.cdc.gov/mmwr/volumes/70/wr/mm7002e1.htm?s_cid=mm7002e1_w) with the authorized and approved COVID-19 vaccines. Fortunately, these reactions are rare, typically occur within minutes of inoculation and can be treated. Approximately 5 per million people vaccinated have experienced anaphylaxis after a COVID-19 vaccine, [according](https://archive.ph/ZnaGT) to the CDC. To make sure serious allergic reactions can be identified and treated, all people receiving a vaccine [should be observed](https://www.cdc.gov/vaccines/covid-19/info-by-product/pfizer/anaphylaxis-management.html) for 15 minutes after getting a shot, and anyone who has experienced anaphylaxis or had any kind of immediate allergic reaction to any vaccine or injection in the past should be monitored for a half hour. People who have had a serious allergic reaction to a previous dose or one of the [vaccine](https://www.fda.gov/media/144414/download) [ingredients](https://www.fda.gov/media/144638/download) [should not](https://www.fda.gov/media/144638/download) be immunized. Also, those who shouldn’t receive one type of COVID-19 vaccine should be monitored for 30 minutes after receiving a different type of vaccine. There is [evidence](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/myocarditis.html) that the Pfizer/BioNTech and Moderna mRNA vaccines may rarely cause inflammation of the heart muscle (myocarditis) or of the surrounding lining (pericarditis), particularly in male adolescents and young adults. Based on [data](https://jamanetwork.com/journals/jama/fullarticle/2788346) collected through August 2021, the reporting rates of either condition in the U.S. are highest in males 16 to 17 years old after the second dose (105.9 cases per million doses of the Pfizer/BioNTech vaccine), followed by 12- to 15-year-old males (70.7 cases per million). The rate for 18- to 24-year-old males was 52.4 cases and 56.3 cases per million doses of Pfizer/BioNTech and Moderna vaccines, respectively. Health officials have [emphasized](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/myocarditis.html) that vaccine-related myocarditis and pericarditis cases are rare and the benefits of vaccination still outweigh the risks. Early evidence [suggests](https://jamanetwork.com/journals/jama/fullarticle/2788346) these myocarditis cases are less severe than typical ones. The CDC has also [noted](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/myocarditis.html) that most patients who were treated “responded well to medicine and rest and felt better quickly.” The Johnson & Johnson vaccine has been linked to an [increased risk](https://archive.ph/ZnaGT) of rare blood clots combined with low levels of blood platelets, especially in women ages [30 to 49](https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2021-12-16/02-COVID-See-508.pdf). Early symptoms of the condition, which is known as thrombosis with thrombocytopenia syndrome, or TTS, can appear as late as three weeks after vaccination and [include](https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html#considerations-Janssen) severe or persistent headaches or blurred vision, leg swelling, and easy bruising or tiny blood spots under the skin outside of the injection site. According to the CDC, TTS has [occurred](https://archive.ph/ZnaGT) in around 4 people per million doses administered. As of [early April](https://archive.ph/vx2mJ), the syndrome has been confirmed in 60 cases, including nine deaths, after more than 18.6 million doses of the J\&J vaccine. Although TTS remains rare, because of the availability of mRNA vaccines, which are not associated with this serious side effect, the FDA on May 5 [limited authorized use](https://perma.cc/T7ZA-EF28) of the J\&J vaccine to adults who either couldn’t get one of the other authorized or approved COVID-19 vaccines because of medical or access reasons, or only wanted a J\&J vaccine for protection against the disease. Several months earlier, [on Dec. 16, 2021](https://www.cdc.gov/media/releases/2021/s1216-covid-19-vaccines.html), the CDC had recommended the Pfizer/BioNTech and Moderna shots over J\&J’s. The J\&J vaccine has also been linked to an [increased risk](https://archive.ph/ZnaGT) of Guillain-Barré Syndrome, a rare disorder in which the immune system attacks nerve cells. [Most people](https://www.cdc.gov/vaccinesafety/concerns/guillain-barre-syndrome.html) who develop GBS fully recover, although some have permanent nerve damage and the condition can be fatal. Safety surveillance data [suggest](https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2791533) that compared with the mRNA vaccines, which have not been linked to GBS, the J\&J vaccine is associated with 15.5 additional GBS cases per million doses of vaccine in the three weeks following vaccination. Most reported cases following J\&J vaccination have occurred in men 50 years old and older. [Link to this](https://www.factcheck.org/scicheck_digest/how-safe-are-the-vaccines/) * ## Full Story COVID-19 vaccines — like all [vaccines](https://www.factcheck.org/scicheck_digest/how-do-we-know-vaccines-are-safe/) and other medical products — come with side effects, including [serious side effects](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html) in rare cases. The vaccines were rolled out to protect people from a novel virus that has [killed](https://www.factcheck.org/2024/01/scicheck-tucker-carlson-video-spreads-falsehoods-on-covid-19-vaccines-who-accord/) millions of people globally and would likely have killed millions more without the arrival of the vaccines. There is a broad consensus from [experts](https://www.who.int/news-room/questions-and-answers/item/coronavirus-disease-\(covid-19\)-vaccines) and [governmental](https://www.fda.gov/news-events/press-announcements/fda-takes-action-updated-mrna-covid-19-vaccines-better-protect-against-currently-circulating) health [agencies](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/safety-of-vaccines.html) that the benefits of COVID-19 vaccination outweigh the risks. Researchers have [scrutinized](https://www.factcheck.org/scicheck_digest/how-safe-are-the-vaccines/) the COVID-19 vaccines’ safety and continue to do so. A [study](https://www.sciencedirect.com/science/article/pii/S0264410X24001270) published Feb. 12 in the journal Vaccine reported on an international group of more than 99 million people who received COVID-19 vaccines, primarily finding links to known rare side effects. The study largely focused on the Pfizer/BioNTech and Moderna vaccines, which have been [widely given](https://covid.cdc.gov/covid-data-tracker/#vaccinations_vacc-people-booster-percent-pop5) in the U.S., as well as the AstraZeneca vaccine, which was [never authorized](https://www.fiercepharma.com/pharma/astrazeneca-withdraws-us-covid-vaccine-application-focus-shifts-antibody-treatments) in the U.S. ![](https://cdn.factcheck.org/UploadedFiles/SciCHECKsquare_4-161x145.png) “What we take away, is that the Covid-19 vaccination campaigns have been very effective in preventing severe disease,” study co-author [Anders Hviid](https://en.ssi.dk/about-us/contact/employees/a/anders-peter-hviid-aii), head of the department of epidemiology research at the Statens Serum Institut in Denmark, told us in an email. “The few serious side effects that we have observed in this and other studies have been rare.” Many popular posts on social media have shared results from the study, some lacking the context that the identified [health problems](https://perma.cc/J8CM-UD26) are [rare](https://perma.cc/Z54H-ESKX), that [most](https://perma.cc/V55U-8326) aren’t [new](https://perma.cc/B93J-XVC5) and that the vaccines have proven benefits. Various posts made unfounded claims, stating or implying that people [should not](https://perma.cc/ST9S-CCAC) have [received](https://perma.cc/6EX7-CFNP) the [vaccines](https://perma.cc/7TKY-2YH7), that the risks [outweigh](https://perma.cc/8QN4-7LVM) the benefits or that the [risk](https://perma.cc/D4UM-WH8C) of the rare side effects is [greater](https://perma.cc/MGK4-Y6CV) than was reported in the study. “Hundreds of millions of people were used as lab rats and now the truth that WE ALL ALREADY KNEW can no longer be denied,” said one popular [post](https://perma.cc/6EX7-CFNP), referring to the vaccines as “experimental” and “UNTESTED.” The post shared a screenshot of the headline of a New York Post [article](https://perma.cc/2VYG-GB9X) about the new study, which read, “COVID vaccines linked to slight increases in heart, brain, blood disorders: study.” “This thing was forced on people who faced almost no risk from Covid,” said another widely read [post](https://perma.cc/4SP3-55WN). “It is completely unacceptable.” The post shared statistics from the paper without making it clear that serious health problems after vaccination were rare and that risk varied by vaccine type and dose. The Vaccine study confirmed that the Moderna and Pfizer/BioNTech vaccines are linked in rare cases to myocarditis and pericarditis, conditions [involving](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html) inflammation of the heart muscle and lining. The rate of myocarditis was most elevated after the second dose of the Moderna vaccine. Myocarditis risk — which is greatest in men in their late teens and early twenties — was [identified](https://www.science.org/content/article/israel-reports-link-between-rare-cases-heart-inflammation-and-covid-19-vaccination) via vaccine safety monitoring and first reported in 2021. Based on the current evidence, the [CDC](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html) says, the benefit of vaccination outweighs the risk of these conditions, which improve for most people after medical treatment and rest. The study confirmed neurological and blood clotting conditions associated with the AstraZeneca vaccine. In the U.S., these [problems](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html) were [linked](https://www.factcheck.org/2021/04/scicheck-qa-on-the-rare-clotting-events-that-caused-the-jj-pause/) to the Johnson & Johnson vaccine, contributing to this vaccine no longer being recommended or available. The study also identified a new possible safety signal indicating a potential link between the first dose of the Moderna and AstraZeneca vaccines and rare neurological conditions. This included an association between the first doses of the vaccines and acute disseminated encephalomyelitis, or ADEM, an autoimmune [condition](https://publications.aap.org/pediatricsinreview/article-abstract/41/7/313/35435/Acute-Transverse-Myelitis-and-Acute-Disseminated) that [causes](https://www.sciencedirect.com/science/article/abs/pii/S0264410X24001269) inflammation of the brain and spinal cord. Hviid emphasized that the researchers only saw these neurological events after first doses of the two vaccines. “We did not see these signals following further doses of these two Covid-19 vaccines, nor did we see them after any dose of the Pfizer/BioNTech vaccine which has been more widely used,” he said. “We are also talking about very rare events,” Hviid continued. “As an example, the association between the first dose of Moderna and acute inflammation of the brain and spine would, if causal, correspond to 1 case per 1.75 million vaccinated. It is only due to the sheer scale of our study, that we have been able to identify this minute potential risk.” ## Study Bolsters the Evidence Serious COVID-19 Vaccine Side Effects Are Rare The Vaccine [study](https://www.sciencedirect.com/science/article/pii/S0264410X24001270#s0095) drew on national or regional health records from eight countries with institutions participating in the [Global Vaccine Data Network](https://globalvaccinedatanetwork.org/ourwork/global-covid-vaccine-safety-gcovs), an international group that studies vaccine safety. The researchers analyzed health outcomes after around 184 million doses of the Pfizer/BioNTech vaccine, 36 million doses of the Moderna vaccine and 23 million doses of the AstraZeneca vaccine. ![](https://cdn.factcheck.org/UploadedFiles/vaccine-400x267-1-1.jpeg) Orathai / [stock.adobe.com](https://stock.adobe.com/) The researchers focused on 13 health problems that either had a known association with vaccination or for which there was some rationale to investigate whether there was an association. To determine whether the health problems were associated with vaccination, they compared the expected rates of the health problems — or the number of health events that should occur based on background rates in the regions studied — with the number of events they observed in the 42 days after vaccination. “This study confirms the primary already detected and validated side effects established by previous literature,” [Jeffrey S. Morris](https://www.dbei.med.upenn.edu/bio/jeffrey-s-morris-phd), director of the division of biostatistics at the University of Pennsylvania’s Perelman School of Medicine, told us via email, referring to the rare heart conditions associated with the Moderna and Pfizer/BioNTech vaccines, as well as the rare conditions associated with the AstraZeneca and Johnson & Johnson vaccines. Morris said that findings on ADEM — the rare autoimmune neurological condition linked to first doses of the Moderna and AstraZeneca vaccines — “might be a new safety signal.” ADEM [involves](https://www.sciencedirect.com/science/article/abs/pii/S0264410X24001269) inflammation to the brain and spinal cord, arising most often in children following an infectious illness. It has a [sudden onset](https://publications.aap.org/pediatricsinreview/article-abstract/41/7/313/35435/Acute-Transverse-Myelitis-and-Acute-Disseminated) and typically eventually improves, with a full recovery in many, although not all, cases. After the first dose of the Moderna vaccine, researchers observed seven ADEM cases, when they expected two. As we’ve said, Hviid calculated the rate of this side effect — if ultimately shown to be related to vaccination — to be 1 in 1.75 million following the first dose of the Moderna vaccine. The data show “this was indeed an EXTREMELY rare adverse event,” Morris said, referring to ADEM. “It is understandable at this incidence rate why it may not have been detected before now, and why a study with 99 million participants like this is important to find even the most rare serious adverse events that are potential minority harm risks of these vaccines.” The authors of the study wrote that more research is needed into ADEM following COVID-19 vaccination, saying that “the number of cases of this rare event were small and the confidence interval wide, so results should be interpreted with caution and confirmed in future studies.” The authors also wrote that neurological [events](https://pubmed.ncbi.nlm.nih.gov/35233819/) have been found to occur at a much higher rate after COVID-19 than after COVID-19 vaccination. The study means that “early warning systems are solid,” said [Marc Veldhoen](https://imm.medicina.ulisboa.pt/investigation/laboratories/marc-veldhoen-lab/#intro), an immunologist at the Instituto de Medicina Molecular João Lobo Antunes in Portugal, in a [post](https://perma.cc/5JKF-QEKL) on X, formerly known as Twitter. “To avoid any adverse reaction is not possible, but, identifying those at higher risk may be possible.” Identifying those at greater risk of side effects can help guide decisions on which vaccines to recommend and what problems doctors should watch for in their patients. *** Editor’s note: SciCheck’s articles providing accurate health information and correcting health misinformation are made possible by a grant from the Robert Wood Johnson Foundation. The foundation has [no control](https://www.factcheck.org/2021/04/scicheck-and-our-committment-to-transparency/) over FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation. ## Sources “[How do we know vaccines are safe?](https://www.factcheck.org/scicheck_digest/how-do-we-know-vaccines-are-safe/)” FactCheck.org. Updated 8 Jul 2021. “[Selected Adverse Events Reported after COVID-19 Vaccination](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html).” CDC website. Updated 12 Sep 2023. Yandell, Kate. “[Tucker Carlson Video Spreads Falsehoods on COVID-19 Vaccines, WHO Accord](https://www.factcheck.org/2024/01/scicheck-tucker-carlson-video-spreads-falsehoods-on-covid-19-vaccines-who-accord/).” FactCheck.org. 13 Jan 2024. “[Safety of COVID-19 Vaccines](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/safety-of-vaccines.html).” CDC website. 3 Nov 2023. “[How safe are the COVID-19 vaccines?](https://www.factcheck.org/scicheck_digest/how-safe-are-the-vaccines/)” FactCheck.org. Updated 17 May 2022. Faksova, K. et al. “[COVID-19 Vaccines and Adverse Events of Special Interest: A Multinational Global Vaccine Data Network (GVDN) Cohort Study of 99 Million Vaccinated Individuals](https://www.sciencedirect.com/science/article/pii/S0264410X24001270).” Vaccine. 12 Feb 2024. COVID Data Tracker. “[COVID-19 Vaccinations in the United States](https://covid.cdc.gov/covid-data-tracker/#vaccinations_vacc-people-booster-percent-pop5).” CDC website. Updated 11 May 2023. Liu, Angus. “[AstraZeneca withdraws US COVID vaccine application, shifts focus to antibody treatments](https://www.fiercepharma.com/pharma/astrazeneca-withdraws-us-covid-vaccine-application-focus-shifts-antibody-treatments).” Fierce Pharma. 10 Nov 2022. Hviid, Anders. Email with FactCheck.org. 22 Feb 2024. TheBlaze. “[Blood clots, neurological disorders, and swollen hearts: Multinational study on COVID vaccines paints a damning picture](https://perma.cc/J8CM-UD26).” Facebook. 20 Feb 2024. Dr. Anthony G. Jay (@anthonygjay). “[I post a lot of vids but rarely PLUG them WATCH my YouTube vid on this – it’s 6 minutes – before it gets taken down 🤐](https://perma.cc/Z54H-ESKX).” Instagram. 20 Feb 2024. bikinibottom\_fish 🐟 (@bikinibottom\_fish). “[Global Study Links COVID-19 Vaccines to Heart and Brain Issues\!](https://perma.cc/V55U-8326)” Instagram. 20 Feb 2024. PatrioticBabe 🇺🇸 (@babedoesthenews). “[❗️](https://perma.cc/B93J-XVC5).” Instagram. 20 Feb 2024. RASPY RAWLS (@raspy\_rawls2). “[… We told yall not to take that shyt but hey wat dew we know 🤷🏾‍♂️ …](https://perma.cc/ST9S-CCAC) .” Instagram. 20 Feb 2024. Jaimee Michell (@thegaywhostrayed). “[I want to know if you think Trump holds any blame, and if not, why not? COMMENT your thoughts BELOW\!](https://perma.cc/6EX7-CFNP)” Instagram. 20 Feb 2024. Liberty Counsel (@libertycounsel). “[…](https://perma.cc/8QN4-7LVM) [“Based on ‘conservative assumptions,’ the estimated harms of the COVID-19 mRNA vaccines ‘greatly outweigh the rewards,’ the article stated, noting that ‘for every life saved, there were nearly 14 times more deaths caused by the modified mRNA injections.’” …](https://perma.cc/8QN4-7LVM)” Instagram. 20 Feb 2024. Shemeka Michelle (@[theshemekamichelle](https://www.instagram.com/theshemekamichelle)). “[Remember when they called them “rare” breakthrough cases? Yeah, me too. \#slight](https://perma.cc/D4UM-WH8C).” Instagram. 20 Feb 2024. Mal’aki (@awake.the.mind). “[‘Slight’ will turn to ‘significant’ soon enough. We tried to warn you all but we’re just crazy conspiracy theorists](https://perma.cc/MGK4-Y6CV).” Instagram. 20 Feb 2024. Steinbuch, Yaron. “[COVID vaccines linked to slight increases in heart, brain, blood disorders: study](https://perma.cc/2VYG-GB9X).” New York Post. 20 Feb 2024. Vogel, Gretchen and Couzin-Frankel, Jennifer. “[Israel reports link between rare cases of heart inflammation and COVID-19 vaccination in young men](https://www.science.org/content/article/israel-reports-link-between-rare-cases-heart-inflammation-and-covid-19-vaccination).” Science. 1 Jun 2021. Robertson, Lori and Kiely, Eugene. “[Q\&A on the Rare Clotting Events That Caused the J\&J Pause](https://www.factcheck.org/2021/04/scicheck-qa-on-the-rare-clotting-events-that-caused-the-jj-pause/).” FactCheck.org. Updated 6 May 2022. Kahn, Ilana. “[Acute Transverse Myelitis and Acute Disseminated Encephalomyelitis](https://publications.aap.org/pediatricsinreview/article-abstract/41/7/313/35435/Acute-Transverse-Myelitis-and-Acute-Disseminated?autologincheck=redirected).” Pediatrics in Review. 1 Jul 2020. Morgan, Hannah J. et al. “[Acute Disseminated Encephalomyelitis and Transverse Myelitis Following COVID-19 Vaccination – A Self-Controlled Case Series Analysis](https://www.sciencedirect.com/science/article/abs/pii/S0264410X24001269).” Vaccine. 12 Feb 2024. “[Global COVID Vaccine Safety (GCoVS)](https://globalvaccinedatanetwork.org/ourwork/global-covid-vaccine-safety-gcovs).” Global Vaccine Data Network website. Accessed 23 Feb 2024. Morris, Jeffrey S. Email with FactCheck.org. 22 Feb 2024. Frontera, Jennifer A. et al. “[Neurological Events Reported after COVID-19 Vaccines: An Analysis of VAERS](https://pubmed.ncbi.nlm.nih.gov/35233819/).” Annals of Neurology. 2 Mar 2022. Marc Veldhoen (@Marc\_Veld). “[COVID-19 vaccines and adverse events of special interest: A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals Anything in those anti-vax stories about large scale damage and deaths due to vaccines? No. …](https://perma.cc/5JKF-QEKL)” X. 19 Feb 2024. - Categories - [Debunking Viral Claims](https://www.factcheck.org/fake-news/) - [FactCheck Posts](https://www.factcheck.org/the-factcheck-wire/) - [SciCheck](https://www.factcheck.org/scicheck/) - Issue - [coronavirus](https://www.factcheck.org/issue/coronavirus/) - [COVID-19 vaccination](https://www.factcheck.org/issue/covid-19-vaccination/) - [myocarditis](https://www.factcheck.org/issue/myocarditis/) - [vaccination](https://www.factcheck.org/issue/vaccination/) - [vaccine safety](https://www.factcheck.org/issue/vaccine-safety/) - Misconceptions - [Distortions of Science](https://www.factcheck.org/misconceptions/distortions-of-science/) - [Vaccination](https://www.factcheck.org/misconceptions/vaccination/) - [Safety](https://www.factcheck.org/misconceptions/safety/) * [Previous StoryPosts Mislead About COVID-19 Vaccine Safety With Out-of-Context Clip of FDA Official](https://www.factcheck.org/2024/02/posts-mislead-about-covid-19-vaccine-safety-with-out-of-context-clip-of-fda-official/) [Next StoryBreaking Down the Immigration Figures](https://www.factcheck.org/2024/02/breaking-down-the-immigration-figures/) * Ask FactCheck Q: I read this on FB. Is it true? The U.S. Treasury just declared the U.S government is insolvent. A: No. That’s the conclusion of an opinion piece that cited a Treasury report showing the government’s liabilities outweigh its assets. But that’s been the case for decades, and unlike an insolvent business, the government can levy taxes. [Read the full question and answer](https://www.factcheck.org/2026/04/the-u-s-treasury-didnt-declare-the-country-insolvent/) [View the Ask FactCheck archives](https://www.factcheck.org/askfactcheck/) Have a question? [Ask us.](https://www.factcheck.org/ask-factcheck/ask-us-a-question/) [Donate Now Because facts matter.](https://giving.aws.cloud.upenn.edu/?fastStart=simpleForm&program=ANS&fund=602014 "Because facts matter.") [![SciCheck's COVID-19/Vaccination Project](https://cdn.factcheck.org/UploadedFiles/misconceptions2.png) SciCheck's COVID-19/Vaccination Project Preempting and exposing vaccination and COVID-19 misinformation.](https://www.factcheck.org/covid-misconceptions/) [![Proyecto de Vacunación/COVID-19](https://cdn.factcheck.org/UploadedFiles/misconceptions2.png) Proyecto de Vacunación/COVID-19 Precaviendo y exponiendo la desinformación sobre el COVID-19 y sus vacunas](https://www.factcheck.org/es/covid-misconceptions/) [![SciCheck](https://cdn.factcheck.org/UploadedFiles/fc-icon-scicheck.png) SciCheck Fact-checking science-based claims.](https://www.factcheck.org/scicheck/) [![Viral Spiral](https://cdn.factcheck.org/UploadedFiles/fc-icon-viralspiral.png) Viral Spiral Don’t get spun by internet rumors.](https://www.factcheck.org/hot-topics/) [![Newsletter](https://cdn.factcheck.org/UploadedFiles/fc-icon-signup.png) Newsletter Get our free weekly email.](https://www.factcheck.org/subscribe) [![Mailbag](https://cdn.factcheck.org/UploadedFiles/fc-icon-mailbag.png) Mailbag Letters from our readers.](https://www.factcheck.org/factcheck-mailbag/) [![On the Air](https://cdn.factcheck.org/UploadedFiles/fc-icon-ota.png) On the Air Our staff on TV and radio.](https://www.factcheck.org/on-the-air) [![NewsFeed Defenders](https://cdn.factcheck.org/UploadedFiles/factchecksidebar_icon-1.png) NewsFeed Defenders A media literacy game to detect misinformation.](https://www.factcheck.org/newsfeed-defenders/) - [Archives](https://www.factcheck.org/archives/) - [Privacy](https://www.factcheck.org/privacy/) - [Copyright Policy](https://www.factcheck.org/copyright-policy/) - [Contact Us](https://www.factcheck.org/about/contact-us/) - [Report Accessibility Issues and Get Help](https://accessibility.web-resources.upenn.edu/get-help) © Copyright 2026 FactCheck.org ® A Project of The Annenberg Public Policy Center of the University of Pennsylvania
Readable Markdown	## SciCheck Digest An international study of around 99 million people confirmed known serious side effects of COVID-19 vaccination. It also identified a possible relationship between the first dose of the Moderna vaccine and a small risk of a neurological condition. Social media posts about the study left out information on the vaccines’ benefits and the rarity of the side effects. * ## Full Story COVID-19 vaccines — like all [vaccines](https://www.factcheck.org/scicheck_digest/how-do-we-know-vaccines-are-safe/) and other medical products — come with side effects, including [serious side effects](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html) in rare cases. The vaccines were rolled out to protect people from a novel virus that has [killed](https://www.factcheck.org/2024/01/scicheck-tucker-carlson-video-spreads-falsehoods-on-covid-19-vaccines-who-accord/) millions of people globally and would likely have killed millions more without the arrival of the vaccines. There is a broad consensus from [experts](https://www.who.int/news-room/questions-and-answers/item/coronavirus-disease-\(covid-19\)-vaccines) and [governmental](https://www.fda.gov/news-events/press-announcements/fda-takes-action-updated-mrna-covid-19-vaccines-better-protect-against-currently-circulating) health [agencies](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/safety-of-vaccines.html) that the benefits of COVID-19 vaccination outweigh the risks. Researchers have [scrutinized](https://www.factcheck.org/scicheck_digest/how-safe-are-the-vaccines/) the COVID-19 vaccines’ safety and continue to do so. A [study](https://www.sciencedirect.com/science/article/pii/S0264410X24001270) published Feb. 12 in the journal Vaccine reported on an international group of more than 99 million people who received COVID-19 vaccines, primarily finding links to known rare side effects. The study largely focused on the Pfizer/BioNTech and Moderna vaccines, which have been [widely given](https://covid.cdc.gov/covid-data-tracker/#vaccinations_vacc-people-booster-percent-pop5) in the U.S., as well as the AstraZeneca vaccine, which was [never authorized](https://www.fiercepharma.com/pharma/astrazeneca-withdraws-us-covid-vaccine-application-focus-shifts-antibody-treatments) in the U.S. ![](https://cdn.factcheck.org/UploadedFiles/SciCHECKsquare_4-161x145.png) “What we take away, is that the Covid-19 vaccination campaigns have been very effective in preventing severe disease,” study co-author [Anders Hviid](https://en.ssi.dk/about-us/contact/employees/a/anders-peter-hviid-aii), head of the department of epidemiology research at the Statens Serum Institut in Denmark, told us in an email. “The few serious side effects that we have observed in this and other studies have been rare.” Many popular posts on social media have shared results from the study, some lacking the context that the identified [health problems](https://perma.cc/J8CM-UD26) are [rare](https://perma.cc/Z54H-ESKX), that [most](https://perma.cc/V55U-8326) aren’t [new](https://perma.cc/B93J-XVC5) and that the vaccines have proven benefits. Various posts made unfounded claims, stating or implying that people [should not](https://perma.cc/ST9S-CCAC) have [received](https://perma.cc/6EX7-CFNP) the [vaccines](https://perma.cc/7TKY-2YH7), that the risks [outweigh](https://perma.cc/8QN4-7LVM) the benefits or that the [risk](https://perma.cc/D4UM-WH8C) of the rare side effects is [greater](https://perma.cc/MGK4-Y6CV) than was reported in the study. “Hundreds of millions of people were used as lab rats and now the truth that WE ALL ALREADY KNEW can no longer be denied,” said one popular [post](https://perma.cc/6EX7-CFNP), referring to the vaccines as “experimental” and “UNTESTED.” The post shared a screenshot of the headline of a New York Post [article](https://perma.cc/2VYG-GB9X) about the new study, which read, “COVID vaccines linked to slight increases in heart, brain, blood disorders: study.” “This thing was forced on people who faced almost no risk from Covid,” said another widely read [post](https://perma.cc/4SP3-55WN). “It is completely unacceptable.” The post shared statistics from the paper without making it clear that serious health problems after vaccination were rare and that risk varied by vaccine type and dose. The Vaccine study confirmed that the Moderna and Pfizer/BioNTech vaccines are linked in rare cases to myocarditis and pericarditis, conditions [involving](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html) inflammation of the heart muscle and lining. The rate of myocarditis was most elevated after the second dose of the Moderna vaccine. Myocarditis risk — which is greatest in men in their late teens and early twenties — was [identified](https://www.science.org/content/article/israel-reports-link-between-rare-cases-heart-inflammation-and-covid-19-vaccination) via vaccine safety monitoring and first reported in 2021. Based on the current evidence, the [CDC](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html) says, the benefit of vaccination outweighs the risk of these conditions, which improve for most people after medical treatment and rest. The study confirmed neurological and blood clotting conditions associated with the AstraZeneca vaccine. In the U.S., these [problems](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html) were [linked](https://www.factcheck.org/2021/04/scicheck-qa-on-the-rare-clotting-events-that-caused-the-jj-pause/) to the Johnson & Johnson vaccine, contributing to this vaccine no longer being recommended or available. The study also identified a new possible safety signal indicating a potential link between the first dose of the Moderna and AstraZeneca vaccines and rare neurological conditions. This included an association between the first doses of the vaccines and acute disseminated encephalomyelitis, or ADEM, an autoimmune [condition](https://publications.aap.org/pediatricsinreview/article-abstract/41/7/313/35435/Acute-Transverse-Myelitis-and-Acute-Disseminated) that [causes](https://www.sciencedirect.com/science/article/abs/pii/S0264410X24001269) inflammation of the brain and spinal cord. Hviid emphasized that the researchers only saw these neurological events after first doses of the two vaccines. “We did not see these signals following further doses of these two Covid-19 vaccines, nor did we see them after any dose of the Pfizer/BioNTech vaccine which has been more widely used,” he said. “We are also talking about very rare events,” Hviid continued. “As an example, the association between the first dose of Moderna and acute inflammation of the brain and spine would, if causal, correspond to 1 case per 1.75 million vaccinated. It is only due to the sheer scale of our study, that we have been able to identify this minute potential risk.” ## Study Bolsters the Evidence Serious COVID-19 Vaccine Side Effects Are Rare The Vaccine [study](https://www.sciencedirect.com/science/article/pii/S0264410X24001270#s0095) drew on national or regional health records from eight countries with institutions participating in the [Global Vaccine Data Network](https://globalvaccinedatanetwork.org/ourwork/global-covid-vaccine-safety-gcovs), an international group that studies vaccine safety. The researchers analyzed health outcomes after around 184 million doses of the Pfizer/BioNTech vaccine, 36 million doses of the Moderna vaccine and 23 million doses of the AstraZeneca vaccine. The researchers focused on 13 health problems that either had a known association with vaccination or for which there was some rationale to investigate whether there was an association. To determine whether the health problems were associated with vaccination, they compared the expected rates of the health problems — or the number of health events that should occur based on background rates in the regions studied — with the number of events they observed in the 42 days after vaccination. “This study confirms the primary already detected and validated side effects established by previous literature,” [Jeffrey S. Morris](https://www.dbei.med.upenn.edu/bio/jeffrey-s-morris-phd), director of the division of biostatistics at the University of Pennsylvania’s Perelman School of Medicine, told us via email, referring to the rare heart conditions associated with the Moderna and Pfizer/BioNTech vaccines, as well as the rare conditions associated with the AstraZeneca and Johnson & Johnson vaccines. Morris said that findings on ADEM — the rare autoimmune neurological condition linked to first doses of the Moderna and AstraZeneca vaccines — “might be a new safety signal.” ADEM [involves](https://www.sciencedirect.com/science/article/abs/pii/S0264410X24001269) inflammation to the brain and spinal cord, arising most often in children following an infectious illness. It has a [sudden onset](https://publications.aap.org/pediatricsinreview/article-abstract/41/7/313/35435/Acute-Transverse-Myelitis-and-Acute-Disseminated) and typically eventually improves, with a full recovery in many, although not all, cases. After the first dose of the Moderna vaccine, researchers observed seven ADEM cases, when they expected two. As we’ve said, Hviid calculated the rate of this side effect — if ultimately shown to be related to vaccination — to be 1 in 1.75 million following the first dose of the Moderna vaccine. The data show “this was indeed an EXTREMELY rare adverse event,” Morris said, referring to ADEM. “It is understandable at this incidence rate why it may not have been detected before now, and why a study with 99 million participants like this is important to find even the most rare serious adverse events that are potential minority harm risks of these vaccines.” The authors of the study wrote that more research is needed into ADEM following COVID-19 vaccination, saying that “the number of cases of this rare event were small and the confidence interval wide, so results should be interpreted with caution and confirmed in future studies.” The authors also wrote that neurological [events](https://pubmed.ncbi.nlm.nih.gov/35233819/) have been found to occur at a much higher rate after COVID-19 than after COVID-19 vaccination. The study means that “early warning systems are solid,” said [Marc Veldhoen](https://imm.medicina.ulisboa.pt/investigation/laboratories/marc-veldhoen-lab/#intro), an immunologist at the Instituto de Medicina Molecular João Lobo Antunes in Portugal, in a [post](https://perma.cc/5JKF-QEKL) on X, formerly known as Twitter. “To avoid any adverse reaction is not possible, but, identifying those at higher risk may be possible.” Identifying those at greater risk of side effects can help guide decisions on which vaccines to recommend and what problems doctors should watch for in their patients. * Editor’s note: SciCheck’s articles providing accurate health information and correcting health misinformation are made possible by a grant from the Robert Wood Johnson Foundation. The foundation has [no control](https://www.factcheck.org/2021/04/scicheck-and-our-committment-to-transparency/) over FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation. ## Sources “[How do we know vaccines are safe?](https://www.factcheck.org/scicheck_digest/how-do-we-know-vaccines-are-safe/)” FactCheck.org. Updated 8 Jul 2021. “[Selected Adverse Events Reported after COVID-19 Vaccination](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html).” CDC website. Updated 12 Sep 2023. Yandell, Kate. “[Tucker Carlson Video Spreads Falsehoods on COVID-19 Vaccines, WHO Accord](https://www.factcheck.org/2024/01/scicheck-tucker-carlson-video-spreads-falsehoods-on-covid-19-vaccines-who-accord/).” FactCheck.org. 13 Jan 2024. “[Safety of COVID-19 Vaccines](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/safety-of-vaccines.html).” CDC website. 3 Nov 2023. “[How safe are the COVID-19 vaccines?](https://www.factcheck.org/scicheck_digest/how-safe-are-the-vaccines/)” FactCheck.org. Updated 17 May 2022. Faksova, K. et al. “[COVID-19 Vaccines and Adverse Events of Special Interest: A Multinational Global Vaccine Data Network (GVDN) Cohort Study of 99 Million Vaccinated Individuals](https://www.sciencedirect.com/science/article/pii/S0264410X24001270).” Vaccine. 12 Feb 2024. COVID Data Tracker. “[COVID-19 Vaccinations in the United States](https://covid.cdc.gov/covid-data-tracker/#vaccinations_vacc-people-booster-percent-pop5).” CDC website. Updated 11 May 2023. Liu, Angus. “[AstraZeneca withdraws US COVID vaccine application, shifts focus to antibody treatments](https://www.fiercepharma.com/pharma/astrazeneca-withdraws-us-covid-vaccine-application-focus-shifts-antibody-treatments).” Fierce Pharma. 10 Nov 2022. Hviid, Anders. Email with FactCheck.org. 22 Feb 2024. TheBlaze. “[Blood clots, neurological disorders, and swollen hearts: Multinational study on COVID vaccines paints a damning picture](https://perma.cc/J8CM-UD26).” Facebook. 20 Feb 2024. Dr. Anthony G. Jay (@anthonygjay). “[I post a lot of vids but rarely PLUG them WATCH my YouTube vid on this – it’s 6 minutes – before it gets taken down 🤐](https://perma.cc/Z54H-ESKX).” Instagram. 20 Feb 2024. bikinibottom\_fish 🐟 (@bikinibottom\_fish). “[Global Study Links COVID-19 Vaccines to Heart and Brain Issues\!](https://perma.cc/V55U-8326)” Instagram. 20 Feb 2024. PatrioticBabe 🇺🇸 (@babedoesthenews). “[❗️](https://perma.cc/B93J-XVC5).” Instagram. 20 Feb 2024. RASPY RAWLS (@raspy\_rawls2). “[… We told yall not to take that shyt but hey wat dew we know 🤷🏾‍♂️ …](https://perma.cc/ST9S-CCAC) .” Instagram. 20 Feb 2024. Jaimee Michell (@thegaywhostrayed). “[I want to know if you think Trump holds any blame, and if not, why not? COMMENT your thoughts BELOW\!](https://perma.cc/6EX7-CFNP)” Instagram. 20 Feb 2024. Liberty Counsel (@libertycounsel). “[…](https://perma.cc/8QN4-7LVM) [“Based on ‘conservative assumptions,’ the estimated harms of the COVID-19 mRNA vaccines ‘greatly outweigh the rewards,’ the article stated, noting that ‘for every life saved, there were nearly 14 times more deaths caused by the modified mRNA injections.’” …](https://perma.cc/8QN4-7LVM)” Instagram. 20 Feb 2024. Shemeka Michelle (@[theshemekamichelle](https://www.instagram.com/theshemekamichelle)). “[Remember when they called them “rare” breakthrough cases? Yeah, me too. \#slight](https://perma.cc/D4UM-WH8C).” Instagram. 20 Feb 2024. Mal’aki (@awake.the.mind). “[‘Slight’ will turn to ‘significant’ soon enough. We tried to warn you all but we’re just crazy conspiracy theorists](https://perma.cc/MGK4-Y6CV).” Instagram. 20 Feb 2024. Steinbuch, Yaron. “[COVID vaccines linked to slight increases in heart, brain, blood disorders: study](https://perma.cc/2VYG-GB9X).” New York Post. 20 Feb 2024. Vogel, Gretchen and Couzin-Frankel, Jennifer. “[Israel reports link between rare cases of heart inflammation and COVID-19 vaccination in young men](https://www.science.org/content/article/israel-reports-link-between-rare-cases-heart-inflammation-and-covid-19-vaccination).” Science. 1 Jun 2021. Robertson, Lori and Kiely, Eugene. “[Q\&A on the Rare Clotting Events That Caused the J\&J Pause](https://www.factcheck.org/2021/04/scicheck-qa-on-the-rare-clotting-events-that-caused-the-jj-pause/).” FactCheck.org. Updated 6 May 2022. Kahn, Ilana. “[Acute Transverse Myelitis and Acute Disseminated Encephalomyelitis](https://publications.aap.org/pediatricsinreview/article-abstract/41/7/313/35435/Acute-Transverse-Myelitis-and-Acute-Disseminated?autologincheck=redirected).” Pediatrics in Review. 1 Jul 2020. Morgan, Hannah J. et al. “[Acute Disseminated Encephalomyelitis and Transverse Myelitis Following COVID-19 Vaccination – A Self-Controlled Case Series Analysis](https://www.sciencedirect.com/science/article/abs/pii/S0264410X24001269).” Vaccine. 12 Feb 2024. “[Global COVID Vaccine Safety (GCoVS)](https://globalvaccinedatanetwork.org/ourwork/global-covid-vaccine-safety-gcovs).” Global Vaccine Data Network website. Accessed 23 Feb 2024. Morris, Jeffrey S. Email with FactCheck.org. 22 Feb 2024. Frontera, Jennifer A. et al. “[Neurological Events Reported after COVID-19 Vaccines: An Analysis of VAERS](https://pubmed.ncbi.nlm.nih.gov/35233819/).” Annals of Neurology. 2 Mar 2022. Marc Veldhoen (@Marc\_Veld). “[COVID-19 vaccines and adverse events of special interest: A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals Anything in those anti-vax stories about large scale damage and deaths due to vaccines? No. …](https://perma.cc/5JKF-QEKL)” X. 19 Feb 2024.
Shard	95 (laksa)
Root Hash	9637418184873233095
Unparsed URL	org,factcheck!www,/2024/02/study-largely-confirms-known-rare-covid-19-vaccine-side-effects/ s443