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1. Shard Calculation

Query:

Response:

Calculated Shard: 110 (from laksa072)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa110.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.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus","crawl_time":1775050186,"first_indexed_time":1615202509,"http_code":200,"src_unparsed":"com,medicalnewstoday!www,\/articles\/pfizer-vaccine-for-coronavirus s443","src_root_hash":"5853625527623639710","history_drop_reason":null,"meta_title":"Pfizer vaccine for coronavirus: Efficacy, side effects, and more","meta_descriptions":["The Pfizer vaccine for the coronavirus SARS-CoV-2 appears to be a safe and effective way to protect against COVID-19. Learn more here."],"attrs_boilerpipe_text":"The Pfizer-BioNTech vaccine is one of several vaccines that can protect against COVID-19. Research indicates that the vaccine has high efficacy in people aged 16 and over.\nThe Pfizer vaccine for COVID-19 is available in the United States and other countries. Side effects are typically mild and last\na few days\n.\nRead on to learn more about the Pfizer vaccine, including how it works, ingredients, effectiveness, and safety.\nThe Pfizer vaccine is a shot that may protect people from developing COVID-19. Its brand name is Comirnaty.\nPfizer Inc., one of the world’s largest biopharmaceutical companies, and BioNTech, a German biotechnology company, created this vaccine.\nAccording to the Centers for Disease Control and Prevention (CDC), people receive this vaccine in two doses, with the second dose coming about\n21 days\nafter the first. However, sometimes, a person may not receive the second dose until 6 weeks after the first.\nThe vaccine works by introducing a molecule to cells, known as messenger RNA (mRNA). This molecule teaches cells to make a protein from the virus that causes COVID-19, which is SARS-CoV-2.\nThe body detects this protein and triggers an immune response. This creates antibodies, as well as longer lasting immunity that can fight off future SARS-CoV-2 infections.\nmRNA\nlipids ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide, 1,2-Distearoyl-sn-glycero-3-phosphocholine, and cholesterol)\nmonobasic potassium phosphate and dibasic sodium phosphate dehydrate, which act as buffers\npotassium chloride and sodium chloride, which are types of salt\nsucrose, or table sugar\nIt does not contain allergens, such as eggs, latex, or preservatives.\nThe FDA has authorized the use of the Pfizer vaccine to prevent COVID-19 in people aged\n12 years of age and older\n.\nMost adults will be eligible for this vaccine. However, some may need to avoid it for safety reasons.\nThe\nCenters for Disease Control and Prevention (CDC)\nadvise that people do not get the Pfizer vaccine if they have had a severe or immediate allergic reaction to any ingredient in an mRNA COVID-19 vaccine, e.g., to polyethylene glycol (PEG) or polysorbate.\nThe CDC define an immediate allergic reaction as a reaction that takes place within 4 hours of exposure, causing symptoms such as:\nhives\nswelling\nwheezing or difficulty breathing\nPeople who have experienced allergic reactions to other vaccines should speak with a healthcare professional before getting a COVID-19 vaccine.\nPeople should also speak with a doctor before getting the Pfizer vaccine if they have:\nother allergies\na\nfever\na bleeding disorder or take medications to thin the blood\na compromised immune system or take medication that affects the immune system\nare pregnant, planning to become pregnant, or are breastfeeding\nhave already received another COVID-19 vaccine\nWhen considering the impact of the Pfizer vaccine, it is important to distinguish between its efficacy and its effectiveness.\n“Efficacy” refers to the vaccine’s performance under ideal and controlled circumstances, such as in clinical trials. “Effectiveness” refers to its performance in real-world situations.\nEfficacy\nThere is strong evidence from clinical trials that the Pfizer vaccine has a high level of efficacy.\nA trial involving 43,548 participants, funded by BioNTech and Pfizer, reported that 2 doses of their vaccine confer\n95% protection\nagainst COVID-19 in people aged 16 years and older.\nEffectiveness\nThis result was consistent across age groups, sexes, races, ethnicities, and body weights, as well as those with underlying medical conditions and people who have already had a SARS-CoV-2 infection.\nA\nlarge study\non the Pfizer vaccine involving about 1.2 million people in Israel supports the findings of clinical trials. It indicates that two doses of the vaccine reduce symptomatic cases of COVID-19 by 94% across all age groups after 7 days of receiving the second dose. The vaccine also reduces severe illness by 92%.\nWhat about new variants?\nIn some parts of the world, new variants of the SARS-CoV-2 virus have emerged. While concerning, this is normal because viruses evolve over time.\nIt is likely that the Pfizer vaccine will still be effective against current variants. A\npreview of a paper\nthat looks at one particular mutation, present in variants first identified in the United Kingdom and South Africa, suggests that the Pfizer vaccine still works against them.\nResearch to date indicates that the Pfizer vaccine is safe for those who are eligible for it. Its manufacturers developed the vaccine according to international safety standards.\nThis vaccine has full authorization from the FDA and the European Medical Association.\nSome people may experience temporary side effects after receiving the Pfizer vaccine, which may last\na few days\n. These include:\npain and swelling around the injection site\nchills\nfever\na\nheadache\ntiredness\nUsually, these side effects indicate that the vaccine is working and are signs that the immune system is responding to it.\nmuscle pain\njoint pain\nnausea\nswollen lymph nodes\nallergic reactions\nSide effects are\nmore common\nafter the second dose than the first dose.\nIf a person experiences side effects after vaccination, they can take steps to care for themselves. Cool compresses and exercising the arm may ease pain and swelling while staying cool, and drinking fluids can help with a fever.\nPeople can also discuss trying over-the-counter (OTC) pain medications, such as acetaminophen, with a doctor or pharmacist.\nIn rare cases, people can experience a severe allergic reaction up to\n60 minutes\nafter receiving the vaccine. Signs and symptoms include:\nbreathing difficulties\ndizziness\nrapid heartbeat\nrash all over the body\nswelling of the face and throat\nweakness\nOther\nrare side effects\nfollowing vaccination can include myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the tissue surrounding the heart). These side effects are more likely following the second dose of the vaccine.\nIf a person experiences any of the above symptoms, dial 911 or call a local emergency department immediately.\nBased on how mRNA vaccines work, the\nCDC\ndo not believe they pose a specific risk during pregnancy. However, there is currently limited evidence to confirm this.\nAnimal studies\non the effects of the Pfizer vaccine found no direct or indirect risks to pregnancy or the health of the fetus. Another mRNA vaccine by Moderna had similar results.\nIn February 2021, Pfizer and BioNTech announced they would begin human trials, testing their COVID-19 vaccine on\n4,000\nhealthy pregnant adult females. These trials are still ongoing.\nIf someone is unsure whether they should get the Pfizer vaccine due to being pregnant, they can discuss their concerns with a doctor. Some may be more comfortable waiting for the results of human trials, while others may want to get a vaccine as soon as they can.\nCOVID-19\ndoes pose\nan increased risk of severe illness during pregnancy.\nThe Moderna and Pfizer vaccines have similar efficacy rates in clinical trials and involve receiving two shots several weeks apart.\nThe table below outlines the differences:\nPfizer\nModerna\nAge\n12 and up\n18 and up\nDosage\ntwo shots, 21 days apart\ntwo shots, 28 days apart\nEfficacy\n95%\nafter two doses\n92%\n14 days after the first dose\nStorage\nIn an ultra-cold freezer at -112°F to -76°F (-80°C to -60°C), or at –\n25°C to -15°C (-13°F to 5°F)\nfor up to 2 weeks\nIn a freezer between -13° F and 5°F, or in the refrigerator between 36°F and 46°F (2°C and 8°C) for up to 30 days\nLarge-scale clinical trials are underway for two other COVID-19 vaccines from:\nAstraZeneca\nNovavax\nThe AstraZeneca vaccination has an efficacy of\n63.09%\nagainst symptomatic COVID-19. It requires two doses, given 8–12 weeks apart. A longer interval in between doses has associations with greater efficacy.\nNovavax reported that their COVID-19 vaccine candidate shows\n89.3%\nefficacy in U.K. phase three trials. Research indicates that the vaccine efficacy might be\n86%\nagainst the variant first identified in the U.K., and 60% against the variant first identified in South Africa.\nThe main benefit of getting a COVID-19 vaccine is protection from the disease, its symptoms, and its complications.\nCOVID-19 has a wide range of effects on the body. For some, it is a mild short-term illness. For others, it is severe and can be life threatening. Some people also go on to experience\nlong COVID\n, which can last for weeks or months.\nPeople who have received a vaccine may also be\nless likely\nto transmit the virus that causes the COVID-19 to other people, reducing the risk of others getting sick, particularly vulnerable people.\nMass vaccination may also allow people to see their friends and family or go back to work sooner. However, no COVID-19 vaccine is 100% effective, so there is still some risk for those who receive a vaccine. Additionally, at present, scientists are unclear how long protection from vaccines lasts.\nEven if a person has received two doses, they\nstill need\nto follow safety guidelines for their local area, such as:\nphysical distancing\nhand washing\nwearing a mask\nGetting a vaccine is not compulsory. However, people who do not get a vaccine are at increased risk of developing COVID-19 than those who receive one.\nSome people are unable to get a COVID-19 vaccine for health reasons. Other people may choose not to.\nThe\nFDA\nstate that it is an individual choice as to whether someone does or does not receive a COVID-19 vaccine. Choosing not to receive a vaccine will not impact their standard of medical care in the U.S.\nPeople who do not get a vaccine should take care to follow safety guidelines to reduce the risk.\nThe Pfizer vaccine for the novel coronavirus, SARS-CoV-2, appears to be effective in clinical trials and real-world situations. Current evidence shows it is safe for most adults.\nCommon side effects include chills, fever, tiredness, headache, and pain or swelling at the injection site. This should only last a few days.\nPeople can discuss different vaccines and their safety with a healthcare professional. People still need to wear masks, practice physical distancing, and follow hygiene guidelines to prevent transmission until advised otherwise.\nFor live updates on the latest developments regarding the novel\ncoronavirus\nand COVID-19, click\nhere\n.","attrs_markdown":"- Health Conditions\n  Health Conditions\n  \n  - [Alzheimer's & Dementia](https:\/\/www.medicalnewstoday.com\/alzheimers-and-dementia)\n  - [Anxiety](https:\/\/www.medicalnewstoday.com\/anxiety)\n  - [Asthma & Allergies](https:\/\/www.medicalnewstoday.com\/asthma-and-allergies)\n  - [Atopic Dermatitis](https:\/\/www.medicalnewstoday.com\/program\/investigating-atopic-dermatitis)\n  - [Breast Cancer](https:\/\/www.medicalnewstoday.com\/breast-cancer)\n  - [Cancer](https:\/\/www.medicalnewstoday.com\/cancer)\n  - [Cardiovascular Health](https:\/\/www.medicalnewstoday.com\/cardiovascular-health)\n  - [COVID-19](https:\/\/www.medicalnewstoday.com\/coronavirus?correlationId=2b137d5a-dcfb-464e-9ea6-72c5a54b4e92)\n  - [Diabetes](https:\/\/www.medicalnewstoday.com\/diabetes)\n  - 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[Ankylosing Spondylitis Pain: Fact or Fiction](https:\/\/www.medicalnewstoday.com\/articles\/complementary-therapies-for-as-quiz#1)\n- Connect\n  About Medical News Today\n  \n  - [Who We Are](https:\/\/www.medicalnewstoday.com\/about)\n  - [Our Editorial Process](https:\/\/www.medicalnewstoday.com\/articles\/process)\n  - [Content Integrity](https:\/\/www.medicalnewstoday.com\/about\/content-integrity)\n  - [Conscious Language](https:\/\/www.medicalnewstoday.com\/about\/conscious-language)\n  \n  Find Community\n  \n  - [Bezzy Breast Cancer](https:\/\/www.bezzybc.com\/lp\/2\/?verzenio&utm_source=mnt&utm_medium=nav-bar-connect)\n  - [Bezzy MS](https:\/\/www.bezzyms.com\/?utm_source=mnt&utm_medium=nav-bar-connect)\n  - [Bezzy Migraine](https:\/\/www.bezzymigraine.com\/?utm_source=mnt&utm_medium=nav-bar-connect)\n  - [Bezzy Psoriasis](https:\/\/www.bezzypsoriasis.com\/?utm_source=mnt&utm_medium=nav-bar-connect)\n  \n  Follow Us\n\nSubscribe\n\n# The Pfizer vaccine for coronavirus\n![](https:\/\/i0.wp.com\/post.medicalnewstoday.com\/wp-content\/uploads\/2022\/01\/Alan-Carter-500x500-Bio.png?w=105&h=105)\n\n[Medically reviewed]() by [Alan Carter, Pharm.D.]() — Written by [Jayne Leonard]() —  [Updated on June 28, 2021]()\n\n- [What it is](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#what-it-is)\n- [How it works](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#how-it-works)\n- [Ingredients](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#ingredients)\n- [Who is eligible?](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#who-is-eligible)\n- [Efficacy](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#efficacy)\n- [Safety](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#safety)\n- [Side effects](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#side-effects)\n- [Pregnancy](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#pregnancy)\n- [Vs. Moderna](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#vs-moderna)\n- [Wider impact](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#wider-impact)\n- [Not having a vaccine](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#not-having-a-vaccine)\n- [Summary](https:\/\/www.medicalnewstoday.com\/articles\/pfizer-vaccine-for-coronavirus#summary)\n\nThe Pfizer-BioNTech vaccine is one of several vaccines that can protect against COVID-19. Research indicates that the vaccine has high efficacy in people aged 16 and over.\n\nThis comes from the *[New England Journal of Medicine](https:\/\/www.nejm.org\/doi\/full\/10.1056\/NEJMoa2034577).*\n\nThe Pfizer vaccine for COVID-19 is available in the United States and other countries. Side effects are typically mild and last [a few days](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/expect\/after.html).\n\nRead on to learn more about the Pfizer vaccine, including how it works, ingredients, effectiveness, and safety.\n\n### Coronavirus resources\nFor more advice on COVID-19 prevention and treatment, visit our [coronavirus hub](https:\/\/www.medicalnewstoday.com\/coronavirus).\n\n## [What is the Pfizer vaccine?]()\n![The silhouette of a hand holding a needle of the Pfizer vaccine, against a backdrop with the Pfizer logo printed across it.](https:\/\/i0.wp.com\/post.medicalnewstoday.com\/wp-content\/uploads\/sites\/3\/2021\/02\/Pfizer_vaccine_GettyImages1231469367_Header-1024x575.jpg?w=1155&h=1528)\n\n[Share on Pinterest](https:\/\/www.pinterest.com\/pin\/create\/button\/?url=https%3A%2F%2Fwww.medicalnewstoday.com%2Farticles%2Fpfizer-vaccine-for-coronavirus&media=https%3A%2F%2Fpost.medicalnewstoday.com%2Fwp-content%2Fuploads%2Fsites%2F3%2F2021%2F02%2FPfizer_vaccine_GettyImages1231469367_Header-1024x575.jpg&description=Pfizer%20vaccine%20for%20coronavirus%3A%20Efficacy%2C%20side%20effects%2C%20and%20more \"Share on Pinterest\")\n\nJaap Arriens\/NurPhoto via Getty Images\n\nThe Pfizer vaccine is a shot that may protect people from developing COVID-19. Its brand name is Comirnaty.\n\nPfizer Inc., one of the world’s largest biopharmaceutical companies, and BioNTech, a German biotechnology company, created this vaccine.\n\nAccording to the Centers for Disease Control and Prevention (CDC), people receive this vaccine in two doses, with the second dose coming about [21 days](https:\/\/www.cdc.gov\/vaccines\/covid-19\/info-by-product\/pfizer\/index.html) after the first. However, sometimes, a person may not receive the second dose until 6 weeks after the first.\n\n## [How does the Pfizer vaccine work?]()\nThe vaccine works by introducing a molecule to cells, known as messenger RNA (mRNA). This molecule teaches cells to make a protein from the virus that causes COVID-19, which is SARS-CoV-2.\n\nThe body detects this protein and triggers an immune response. This creates antibodies, as well as longer lasting immunity that can fight off future SARS-CoV-2 infections.\n\n[Learn more about how mRNA vaccines work.](https:\/\/www.medicalnewstoday.com\/articles\/what-is-a-vaccine)\n\n## [What does the vaccine contain?]()\nThe [Food and Drug Administration (FDA)](https:\/\/www.fda.gov\/media\/144414\/download) state that the Pfizer vaccine contains:\n\n- mRNA\n- lipids ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2\\[(polyethylene glycol)-2000\\]-N,N-ditetradecylacetamide, 1,2-Distearoyl-sn-glycero-3-phosphocholine, and cholesterol)\n- monobasic potassium phosphate and dibasic sodium phosphate dehydrate, which act as buffers\n- potassium chloride and sodium chloride, which are types of salt\n- sucrose, or table sugar\n\nIt does not contain allergens, such as eggs, latex, or preservatives.\n\n[Learn more about allergies and allergens here.](https:\/\/www.medicalnewstoday.com\/articles\/264419)\n\n## [Who can have the Pfizer vaccine?]()\nThe FDA has authorized the use of the Pfizer vaccine to prevent COVID-19 in people aged [12 years of age and older](https:\/\/www.fda.gov\/media\/144414\/download).\n\nMost adults will be eligible for this vaccine. However, some may need to avoid it for safety reasons.\n\nThe [Centers for Disease Control and Prevention (CDC)](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/different-vaccines\/Pfizer-BioNTech.html) advise that people do not get the Pfizer vaccine if they have had a severe or immediate allergic reaction to any ingredient in an mRNA COVID-19 vaccine, e.g., to polyethylene glycol (PEG) or polysorbate.\n\nThe CDC define an immediate allergic reaction as a reaction that takes place within 4 hours of exposure, causing symptoms such as:\n\n- [hives](https:\/\/www.medicalnewstoday.com\/articles\/157260)\n- swelling\n- wheezing or difficulty breathing\n\nPeople who have experienced allergic reactions to other vaccines should speak with a healthcare professional before getting a COVID-19 vaccine.\n\nPeople should also speak with a doctor before getting the Pfizer vaccine if they have:\n\n- other allergies\n- a [fever](https:\/\/www.medicalnewstoday.com\/articles\/168266)\n- a bleeding disorder or take medications to thin the blood\n- a compromised immune system or take medication that affects the immune system\n- are pregnant, planning to become pregnant, or are breastfeeding\n- have already received another COVID-19 vaccine\n\n[Learn more about getting the COVID-19 vaccination here.](http:\/\/articles\/coronavirus-vaccine)\n\n## [How effective is the Pfizer vaccine?]()\nWhen considering the impact of the Pfizer vaccine, it is important to distinguish between its efficacy and its effectiveness.\n\n“Efficacy” refers to the vaccine’s performance under ideal and controlled circumstances, such as in clinical trials. “Effectiveness” refers to its performance in real-world situations.\n\n### Efficacy\nThere is strong evidence from clinical trials that the Pfizer vaccine has a high level of efficacy.\n\nA trial involving 43,548 participants, funded by BioNTech and Pfizer, reported that 2 doses of their vaccine confer [95% protection](https:\/\/www.nejm.org\/doi\/full\/10.1056\/NEJMoa2034577) against COVID-19 in people aged 16 years and older.\n\n### Effectiveness\nThis result was consistent across age groups, sexes, races, ethnicities, and body weights, as well as those with underlying medical conditions and people who have already had a SARS-CoV-2 infection.\n\nA [large study](https:\/\/www.nejm.org\/doi\/full\/10.1056\/NEJMoa2101765) on the Pfizer vaccine involving about 1.2 million people in Israel supports the findings of clinical trials. It indicates that two doses of the vaccine reduce symptomatic cases of COVID-19 by 94% across all age groups after 7 days of receiving the second dose. The vaccine also reduces severe illness by 92%.\n\n### What about new variants?\nIn some parts of the world, new variants of the SARS-CoV-2 virus have emerged. While concerning, this is normal because viruses evolve over time.\n\nIt is likely that the Pfizer vaccine will still be effective against current variants. A [preview of a paper](https:\/\/www.biorxiv.org\/content\/10.1101\/2021.01.07.425740v1) that looks at one particular mutation, present in variants first identified in the United Kingdom and South Africa, suggests that the Pfizer vaccine still works against them.\n\n[Find out more about vaccines and how they work here.](https:\/\/www.medicalnewstoday.com\/articles\/what-is-a-vaccine)\n\n## [Safety]()\nResearch to date indicates that the Pfizer vaccine is safe for those who are eligible for it. Its manufacturers developed the vaccine according to international safety standards.\n\nThis vaccine has full authorization from the FDA and the European Medical Association.\n\n## [Side effects]()\nSome people may experience temporary side effects after receiving the Pfizer vaccine, which may last [a few days](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/expect\/after.html). These include:\n\n- pain and swelling around the injection site\n- chills\n- fever\n- a [headache](https:\/\/www.medicalnewstoday.com\/articles\/73936)\n- [tiredness](https:\/\/www.medicalnewstoday.com\/articles\/248002)\n\nUsually, these side effects indicate that the vaccine is working and are signs that the immune system is responding to it.\n\n[Less commonly](https:\/\/www.fda.gov\/media\/144414\/download), people experience:\n\n- muscle pain\n- joint pain\n- nausea\n- swollen lymph nodes\n- allergic reactions\n\nSide effects are [more common](https:\/\/www.fda.gov\/emergency-preparedness-and-response\/coronavirus-disease-2019-covid-19\/pfizer-biontech-covid-19-vaccine) after the second dose than the first dose.\n\nIf a person experiences side effects after vaccination, they can take steps to care for themselves. Cool compresses and exercising the arm may ease pain and swelling while staying cool, and drinking fluids can help with a fever.\n\nPeople can also discuss trying over-the-counter (OTC) pain medications, such as acetaminophen, with a doctor or pharmacist.\n\nIn rare cases, people can experience a severe allergic reaction up to [60 minutes](https:\/\/www.ncbi.nlm.nih.gov\/pmc\/articles\/PMC7808711\/) after receiving the vaccine. Signs and symptoms include:\n\n- breathing difficulties\n- dizziness\n- rapid heartbeat\n- rash all over the body\n- swelling of the face and throat\n- weakness\n\nOther [rare side effects](https:\/\/www.fda.gov\/news-events\/press-announcements\/coronavirus-covid-19-update-june-25-2021) following vaccination can include myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the tissue surrounding the heart). These side effects are more likely following the second dose of the vaccine.\n\nIf a person experiences any of the above symptoms, dial 911 or call a local emergency department immediately.\n\n[Learn more about the safety and other facts about COVID-19 vaccinations here.](https:\/\/www.medicalnewstoday.com\/articles\/coronavirus-vaccine)\n\n## [Safety during pregnancy]()\nBased on how mRNA vaccines work, the [CDC](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/recommendations\/pregnancy.html) do not believe they pose a specific risk during pregnancy. However, there is currently limited evidence to confirm this.\n\n[Animal studies](https:\/\/www.acog.org\/covid-19\/covid-19-vaccines-and-pregnancy-conversation-guide-for-clinicians) on the effects of the Pfizer vaccine found no direct or indirect risks to pregnancy or the health of the fetus. Another mRNA vaccine by Moderna had similar results.\n\nIn February 2021, Pfizer and BioNTech announced they would begin human trials, testing their COVID-19 vaccine on [4,000](https:\/\/www.pfizer.com\/news\/press-release\/press-release-detail\/pfizer-and-biontech-commence-global-clinical-trial-evaluate) healthy pregnant adult females. These trials are still ongoing.\n\nIf someone is unsure whether they should get the Pfizer vaccine due to being pregnant, they can discuss their concerns with a doctor. Some may be more comfortable waiting for the results of human trials, while others may want to get a vaccine as soon as they can.\n\nCOVID-19 [does pose](https:\/\/www.acog.org\/covid-19\/covid-19-vaccines-and-pregnancy-conversation-guide-for-clinicians) an increased risk of severe illness during pregnancy.\n\n[Learn more about how COVID-19 affects pregnancy here.](https:\/\/www.medicalnewstoday.com\/articles\/covid-19-during-pregnancy-how-the-placenta-is-involved)\n\n## [Comparison to the Moderna vaccine]()\nThe Moderna and Pfizer vaccines have similar efficacy rates in clinical trials and involve receiving two shots several weeks apart.\n\nThe table below outlines the differences:\n\n|   | **Pfizer** | **Moderna** |\n|---|---|---|\n| **Age** | [12 and up](https:\/\/www.cdc.gov\/vaccines\/covid-19\/info-by-product\/pfizer\/index.html) | [18 and up](https:\/\/www.cdc.gov\/vaccines\/covid-19\/info-by-product\/moderna\/index.html) |\n| **Dosage** | two shots, 21 days apart | two shots, 28 days apart |\n| **Efficacy** | [95%](https:\/\/www.nejm.org\/doi\/full\/10.1056\/NEJMoa2034577) after two doses | [92%](https:\/\/www.who.int\/news-room\/feature-stories\/detail\/the-moderna-covid-19-mrna-1273-vaccine-what-you-need-to-know) 14 days after the first dose |\n| **Storage** | In an ultra-cold freezer at -112°F to -76°F (-80°C to -60°C), or at –[25°C to -15°C (-13°F to 5°F)](https:\/\/www.fda.gov\/media\/144413\/download) for up to 2 weeks | In a freezer between -13° F and 5°F, or in the refrigerator between 36°F and 46°F (2°C and 8°C) for up to 30 days |\n\nLarge-scale clinical trials are underway for two other COVID-19 vaccines from:\n\n- AstraZeneca\n- Novavax\n\nThe AstraZeneca vaccination has an efficacy of [63\\.09%](https:\/\/www.who.int\/news-room\/feature-stories\/detail\/the-oxford-astrazeneca-covid-19-vaccine-what-you-need-to-know) against symptomatic COVID-19. It requires two doses, given 8–12 weeks apart. A longer interval in between doses has associations with greater efficacy.\n\nNovavax reported that their COVID-19 vaccine candidate shows [89\\.3%](https:\/\/ir.novavax.com\/news-releases\/news-release-details\/novavax-covid-19-vaccine-demonstrates-893-efficacy-uk-phase-3) efficacy in U.K. phase three trials. Research indicates that the vaccine efficacy might be [86%](https:\/\/www.bmj.com\/content\/372\/bmj.n296) against the variant first identified in the U.K., and 60% against the variant first identified in South Africa.\n\n[Learn more about the Moderna vaccine here](https:\/\/www.medicalnewstoday.com\/articles\/moderna-vaccine-for-coronavirus).\n\n## [Impact]()\nThe main benefit of getting a COVID-19 vaccine is protection from the disease, its symptoms, and its complications.\n\nCOVID-19 has a wide range of effects on the body. For some, it is a mild short-term illness. For others, it is severe and can be life threatening. Some people also go on to experience [long COVID](https:\/\/www.medicalnewstoday.com\/articles\/long-term-effects-of-coronavirus), which can last for weeks or months.\n\nPeople who have received a vaccine may also be [less likely](https:\/\/www.who.int\/news-room\/q-a-detail\/coronavirus-disease-\\(covid-19\\)-vaccines) to transmit the virus that causes the COVID-19 to other people, reducing the risk of others getting sick, particularly vulnerable people.\n\nMass vaccination may also allow people to see their friends and family or go back to work sooner. However, no COVID-19 vaccine is 100% effective, so there is still some risk for those who receive a vaccine. Additionally, at present, scientists are unclear how long protection from vaccines lasts.\n\nEven if a person has received two doses, they [still need](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/faq.html) to follow safety guidelines for their local area, such as:\n\n- physical distancing\n- hand washing\n- wearing a mask\n\n[Learn more tips for preventing the spread of SARS-CoV-2.](https:\/\/www.medicalnewstoday.com\/articles\/coronavirus-prevention)\n\n## [What happens if you do not get a vaccine?]()\nGetting a vaccine is not compulsory. However, people who do not get a vaccine are at increased risk of developing COVID-19 than those who receive one.\n\nSome people are unable to get a COVID-19 vaccine for health reasons. Other people may choose not to.\n\nThe [FDA](https:\/\/www.fda.gov\/media\/144638\/download) state that it is an individual choice as to whether someone does or does not receive a COVID-19 vaccine. Choosing not to receive a vaccine will not impact their standard of medical care in the U.S.\n\nPeople who do not get a vaccine should take care to follow safety guidelines to reduce the risk.\n\n## [Summary]()\nThe Pfizer vaccine for the novel coronavirus, SARS-CoV-2, appears to be effective in clinical trials and real-world situations. Current evidence shows it is safe for most adults.\n\nCommon side effects include chills, fever, tiredness, headache, and pain or swelling at the injection site. This should only last a few days.\n\nPeople can discuss different vaccines and their safety with a healthcare professional. People still need to wear masks, practice physical distancing, and follow hygiene guidelines to prevent transmission until advised otherwise.\n\n***For live updates on the latest developments regarding the novel [coronavirus](https:\/\/www.medicalnewstoday.com\/articles\/256521) and COVID-19, click [here](https:\/\/www.medicalnewstoday.com\/articles\/live-updates-coronavirus-covid-19)***.\n\n- [Flu \/ Cold \/ SARS](https:\/\/www.medicalnewstoday.com\/categories\/flu-sars)\n- [Immune System \/ Vaccines](https:\/\/www.medicalnewstoday.com\/categories\/immune-system)\n- [Infectious Diseases \/ Bacteria \/ Viruses](https:\/\/www.medicalnewstoday.com\/categories\/infectious_diseases)\n- [COVID-19](https:\/\/www.medicalnewstoday.com\/categories\/covid-19)\n- [Cat 1](https:\/\/www.medicalnewstoday.com\/categories\/cat1-en)\n\n### How we reviewed this article:\nSources\n\nMedical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our [editorial policy](https:\/\/www.medicalnewstoday.com\/articles\/process).\n\n- Allergic reactions including anaphylaxis after receipt of the first dose of Pfizer-BioNTech COVID-19 vaccine. (2021).  \n  <https:\/\/www.ncbi.nlm.nih.gov\/pmc\/articles\/PMC7808711\/>\n- Coronavirus (COVID-19) update: FDA Allows more flexible storage, transportation conditions for Pfizer-BioNTech COVID-19 vaccine. (2021).  \n  <https:\/\/www.fda.gov\/news-events\/press-announcements\/coronavirus-covid-19-update-fda-allows-more-flexible-storage-transportation-conditions-pfizer>\n- Coronavirus (COVID-19) update: FDA limits use of Janssen COVID-19 vaccine to certain individuals. (2022).  \n  <https:\/\/www.fda.gov\/news-events\/press-announcements\/coronavirus-covid-19-update-fda-limits-use-janssen-covid-19-vaccine-certain-individuals>\n- Coronavirus disease (COVID-19): Vaccines. (2020).  \n  <https:\/\/www.who.int\/news-room\/q-a-detail\/coronavirus-disease-(covid-19)-vaccines>\n- Coronavirus (COVID-19) update: June 25, 2021. (2021).  \n  <https:\/\/www.fda.gov\/news-events\/press-announcements\/coronavirus-covid-19-update-june-25-2021>\n- COVID-19 vaccines and pregnancy: Conversation guide for clinicians. (n.d.).  \n  <https:\/\/www.acog.org\/covid-19\/covid-19-vaccines-and-pregnancy-conversation-guide-for-clinicians>\n- Dagan, N., *et al.* (2021). BNT162b2 mRNA Covid-19 vaccine in a nationwide mass vaccination setting.  \n  <https:\/\/www.nejm.org\/doi\/full\/10.1056\/NEJMoa2101765>\n- Different COVID-19 vaccines. (2021).  \n  <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/different-vaccines.html>\n- EMA recommends first COVID-19 vaccine for authorisation in the EU. (2020).  \n  <https:\/\/www.ema.europa.eu\/en\/news\/ema-recommends-first-covid-19-vaccine-authorisation-eu>\n- Fact sheet for healthcare providers administering vaccination (vaccination providers). Emergency use authorization (EUA) of the Pfizer-Biontech COVID-19 vaccine to prevent coronavirus disease 2019 (COVID-19) \\[Fact sheet\\]. (2021).  \n  <https:\/\/www.fda.gov\/media\/144413\/download>\n- Fact sheet for recipients and caregivers. Emergency use authorization (EUA) of the Moderna COVID-19 vaccine to prevent coronavirus disease 2019 (COVID-19) in individuals 18 years of age and older. (2020).  \n  <https:\/\/www.fda.gov\/media\/144638\/download>\n- FDA briefing document: Moderna COVID-19 vaccine. (2020).  \n  <https:\/\/www.fda.gov\/media\/144434\/download>\n- Frequently asked questions about COVID-19 vaccination. (2021).  \n  <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/faq.html>\n- Information about the Pfizer-BioNTech COVID-19 vaccine. (2021).  \n  <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/different-vaccines\/Pfizer-BioNTech.html>\n- Janssen COVID-19 vaccine. (2022).  \n  <https:\/\/www.fda.gov\/emergency-preparedness-and-response\/coronavirus-disease-2019-covid-19\/janssen-covid-19-vaccine>\n- Johnson & Johnson announces single-shot Janssen COVID-19 vaccine candidate met primary endpoints in interim analysis of its phase 3 ENSEMBLE trial. (2021).  \n  <https:\/\/www.jnj.com\/johnson-johnson-announces-single-shot-janssen-covid-19-vaccine-candidate-met-primary-endpoints-in-interim-analysis-of-its-phase-3-ensemble-trial>\n- Johnson & Johnson. (2021). Johnson & Johnson COVID-19 vaccine authorized by U.S. FDA for emergency use – first single-shot vaccine in fight against global pandemic \\[Press release\\].  \n  <https:\/\/www.jnj.com\/johnson-johnson-covid-19-vaccine-authorized-by-u-s-fda-for-emergency-usefirst-single-shot-vaccine-in-fight-against-global-pandemic>\n- Mahase, E. (2021). COVID-19: Assess the effects of extending Pfizer vaccine dosing interval, expert urges.  \n  <https:\/\/www.bmj.com\/content\/372\/bmj.n162>\n- Mahase, E. (2021). COVID-19: Novavax vaccine efficacy is 86% against UK variant and 60% against South African variant.  \n  <https:\/\/www.bmj.com\/content\/372\/bmj.n296>\n- Mahase, E. (2020). Covid-19: Pfizer vaccine efficacy was 52% after first dose and 95% after second dose, paper shows.  \n  <https:\/\/www.bmj.com\/content\/371\/bmj.m4826>\n- Mahase, E. (2021). COVID-19: Reports from Israel suggest one dose of Pfizer vaccine could be less effective than expected.  \n  <https:\/\/www.bmj.com\/content\/372\/bmj.n217>\n- Moderna COVID-19 vaccine. (2021).  \n  <https:\/\/www.cdc.gov\/vaccines\/covid-19\/info-by-product\/moderna\/index.html>\n- Novavax. (2021). Novavax COVID-19 vaccine demonstrates 89.3% efficacy in UK phase 3 tria \\[Press release\\].  \n  <https:\/\/ir.novavax.com\/news-releases\/news-release-details\/novavax-covid-19-vaccine-demonstrates-893-efficacy-uk-phase-3>\n- Pfizer. (2021). Pfizer and BioNTech commence global clinical trial to evaluate COVID-19 vaccine in pregnant women \\[Press release\\].  \n  <https:\/\/www.pfizer.com\/news\/press-release\/press-release-detail\/pfizer-and-biontech-commence-global-clinical-trial-evaluate>\n- Pfizer-BioNTech COVID-19 vaccine. (2021).  \n  <https:\/\/www.cdc.gov\/vaccines\/covid-19\/info-by-product\/pfizer\/index.html>\n- Pfizer-BioNTech COVID-19 vaccine. (2021).  \n  <https:\/\/www.fda.gov\/emergency-preparedness-and-response\/coronavirus-disease-2019-covid-19\/pfizer-biontech-covid-19-vaccine>\n- Pfizer-BioNTech COVID-19 Vaccine EUA fact sheet for recipients and caregivers. (2021).  \n  <https:\/\/www.fda.gov\/media\/144414\/download>\n- Polack, F. P., *et al.* (2020). Safety and efficacy of the BNT162b2 mRNA Covid-19 vaccine.  \n  <https:\/\/www.nejm.org\/doi\/full\/10.1056\/NEJMoa2034577>\n- Possible side effects after getting a COVID-19 vaccine (2021).  \n  <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/expect\/after.html>\n- Singal, A. G., *et al.* (2014). A primer on effectiveness and efficacy trials.  \n  <https:\/\/www.ncbi.nlm.nih.gov\/pmc\/articles\/PMC3912314\/>\n- The Advisory Committee on Immunization Practices’ interim recommendation for use of Pfizer-BioNTech COVID-19 vaccine. (2020).  \n  <https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm6950e2.htm>\n- The Moderna COVID-19 (mRNA-1273) vaccine: What you need to know. (2021).  \n  <https:\/\/www.who.int\/news-room\/feature-stories\/detail\/the-moderna-covid-19-mrna-1273-vaccine-what-you-need-to-know>\n- The Oxford\/AstraZeneca COVID-19 vaccine: What you need to know. (2021).  \n  <https:\/\/www.who.int\/news-room\/feature-stories\/detail\/the-oxford-astrazeneca-covid-19-vaccine-what-you-need-to-know>\n- Understanding mRNA COVID-19 vaccines. (2020).  \n  <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/different-vaccines\/mrna.html>\n- Vaccination considerations for people who are pregnant or breastfeeding. (2021).  \n  <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/recommendations\/pregnancy.html>\n- Xie, X., *et al.* (2021). Neutralization of N501Y mutant SARS-CoV-2 by BNT162b2 vaccine-elicited sera.  \n  <https:\/\/www.biorxiv.org\/content\/10.1101\/2021.01.07.425740v1>\n\nShare this article\n\n![](https:\/\/i0.wp.com\/post.medicalnewstoday.com\/wp-content\/uploads\/2022\/01\/Alan-Carter-500x500-Bio.png?w=105&h=105)\n\n[Medically reviewed]() by [Alan Carter, Pharm.D.]() — Written by [Jayne Leonard]() —  [Updated on June 28, 2021]()\n\n## Latest news\n- [Could probiotics, dietary changes help protect brain health as we age?](https:\/\/www.medicalnewstoday.com\/articles\/could-probiotics-dietary-changes-help-protect-brain-health-as-we-age)\n- [9 steps to improve heart health, per new dietary guidance from AHA](https:\/\/www.medicalnewstoday.com\/articles\/9-steps-improve-heart-health-diet-guidance-aha)\n- [AI model can accurately predict liver cancer risk, study suggests](https:\/\/www.medicalnewstoday.com\/articles\/ai-model-accurately-predict-liver-cancer-risk)\n- [AI-powered stroke tool linked to improved patient outcomes in large clinical trial](https:\/\/www.medicalnewstoday.com\/articles\/ai-powered-stroke-tool-linked-improved-patient-outcomes-large-clinical-trial)\n- [Eating same meals on repeat, and more at weekends may help you lose more weight](https:\/\/www.medicalnewstoday.com\/articles\/eating-same-meals-repeat-more-weekends-may-help-lose-more-weight)\n\n### Related Coverage\n- [Coronavirus (COVID-19) vaccine: What to know](https:\/\/www.medicalnewstoday.com\/articles\/coronavirus-vaccine?utm_source=ReadNext)\n  \n  Medically reviewed by [Avi Varma, MD, MPH, AAHIVS, FAAFP](https:\/\/www.medicalnewstoday.com\/reviewers)\n  \n  [COVID-19 vaccines help prevent illness, particularly in vulnerable groups. Read about recommendations, how to get a vaccine, and vaccine safety.](https:\/\/www.medicalnewstoday.com\/articles\/coronavirus-vaccine?utm_source=ReadNext)\n  \n  [READ MORE](https:\/\/www.medicalnewstoday.com\/articles\/coronavirus-vaccine?utm_source=ReadNext)\n- [Are treatments available for COVID-19?](https:\/\/www.medicalnewstoday.com\/articles\/coronavirus-treatment?utm_source=ReadNext)\n  \n  Medically reviewed by [Cameron White, M.D., MPH](https:\/\/www.medicalnewstoday.com\/reviewers)\n  \n  [Researchers worldwide are working to develop treatments for COVID-19, the disease that the novel coronavirus causes. Learn about the latest treatment…](https:\/\/www.medicalnewstoday.com\/articles\/coronavirus-treatment?utm_source=ReadNext)\n  \n  [READ MORE](https:\/\/www.medicalnewstoday.com\/articles\/coronavirus-treatment?utm_source=ReadNext)\n- [What are the long-term effects of COVID-19?](https:\/\/www.medicalnewstoday.com\/articles\/long-term-effects-of-coronavirus?utm_source=ReadNext)\n  \n  Medically reviewed by [Joseph Vinetz, MD](https:\/\/www.medicalnewstoday.com\/reviewers)\n  \n  [COVID-19 can cause lasting symptoms, complications, and distress, and doctors are still unsure of the full scope of the long-term effects. Learn more…](https:\/\/www.medicalnewstoday.com\/articles\/long-term-effects-of-coronavirus?utm_source=ReadNext)\n  \n  [READ MORE](https:\/\/www.medicalnewstoday.com\/articles\/long-term-effects-of-coronavirus?utm_source=ReadNext)\n- [All you need to know about COVID-19](https:\/\/www.medicalnewstoday.com\/articles\/covid-19?utm_source=ReadNext)\n  \n  Medically reviewed by [Meredith Goodwin, MD, FAAFP](https:\/\/www.medicalnewstoday.com\/reviewers)\n  \n  [COVID-19 is a highly contagious infectious disease resulting from a recently identified coronavirus. Learn to curb its spread and more here.](https:\/\/www.medicalnewstoday.com\/articles\/covid-19?utm_source=ReadNext)\n  \n  [READ MORE](https:\/\/www.medicalnewstoday.com\/articles\/covid-19?utm_source=ReadNext)\n- [What are the symptoms of COVID-19?](https:\/\/www.medicalnewstoday.com\/articles\/covid-19-symptoms?utm_source=ReadNext)\n  \n  Medically reviewed by [Joseph Vinetz, MD](https:\/\/www.medicalnewstoday.com\/reviewers)\n  \n  [The main symptoms of COVID-19 are fever, dry cough, and shortness of breath. Learn more about the other symptoms and what to expect here.](https:\/\/www.medicalnewstoday.com\/articles\/covid-19-symptoms?utm_source=ReadNext)\n  \n  [READ MORE](https:\/\/www.medicalnewstoday.com\/articles\/covid-19-symptoms?utm_source=ReadNext)\n\n© 2026 Healthline Media UK Ltd, London, UK. All rights reserved. MNT is the registered trade mark of Healthline Media. Healthline Media is an RVO Health Company. 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Healthline Media is an RVO Health Company. Any medical information published on this website is not intended as a substitute for informed medical advice and you should not take any action before consulting with a healthcare professional. [See additional information](https:\/\/www.medicalnewstoday.com\/about\/additional-information).\n\n© 2026 Healthline Media UK Ltd, London, UK. All rights reserved. MNT is the registered trade mark of Healthline Media. Healthline Media is an RVO Health Company. Any medical information published on this website is not intended as a substitute for informed medical advice and you should not take any action before consulting with a healthcare professional. [See additional information](https:\/\/www.medicalnewstoday.com\/about\/additional-information).\n\n[About](https:\/\/www.healthlinemedia.com\/?utm_source=medicalnewstoday.com&utm_medium=site&utm_campaign=footer&utm_content=about)[Careers](https:\/\/rvohealth.com\/careers)[Advertise with us](https:\/\/www.healthlinemedia.com\/advertise?utm_source=medicalnewstoday.com&utm_medium=site&utm_campaign=footer&utm_content=advertise)\n\nOUR BRANDS\n\n[Healthline](https:\/\/www.healthline.com\/)[Medical News Today](https:\/\/www.medicalnewstoday.com\/)[Greatist](https:\/\/greatist.com\/)[Psych Central](https:\/\/psychcentral.com\/)[Bezzy](https:\/\/bezzy.com\/)\n\n![](http:\/\/b.scorecardresearch.com\/p?c1=2&c2=38584006&cv=3.9&cj=1&comscorekw=main)","attrs_readable_markdown":"The Pfizer-BioNTech vaccine is one of several vaccines that can protect against COVID-19. Research indicates that the vaccine has high efficacy in people aged 16 and over.\n\nThe Pfizer vaccine for COVID-19 is available in the United States and other countries. Side effects are typically mild and last [a few days](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/expect\/after.html).\n\nRead on to learn more about the Pfizer vaccine, including how it works, ingredients, effectiveness, and safety.\n\nThe Pfizer vaccine is a shot that may protect people from developing COVID-19. Its brand name is Comirnaty.\n\nPfizer Inc., one of the world’s largest biopharmaceutical companies, and BioNTech, a German biotechnology company, created this vaccine.\n\nAccording to the Centers for Disease Control and Prevention (CDC), people receive this vaccine in two doses, with the second dose coming about [21 days](https:\/\/www.cdc.gov\/vaccines\/covid-19\/info-by-product\/pfizer\/index.html) after the first. However, sometimes, a person may not receive the second dose until 6 weeks after the first.\n\nThe vaccine works by introducing a molecule to cells, known as messenger RNA (mRNA). This molecule teaches cells to make a protein from the virus that causes COVID-19, which is SARS-CoV-2.\n\nThe body detects this protein and triggers an immune response. This creates antibodies, as well as longer lasting immunity that can fight off future SARS-CoV-2 infections.\n\n- mRNA\n- lipids ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2\\[(polyethylene glycol)-2000\\]-N,N-ditetradecylacetamide, 1,2-Distearoyl-sn-glycero-3-phosphocholine, and cholesterol)\n- monobasic potassium phosphate and dibasic sodium phosphate dehydrate, which act as buffers\n- potassium chloride and sodium chloride, which are types of salt\n- sucrose, or table sugar\n\nIt does not contain allergens, such as eggs, latex, or preservatives.\n\nThe FDA has authorized the use of the Pfizer vaccine to prevent COVID-19 in people aged [12 years of age and older](https:\/\/www.fda.gov\/media\/144414\/download).\n\nMost adults will be eligible for this vaccine. However, some may need to avoid it for safety reasons.\n\nThe [Centers for Disease Control and Prevention (CDC)](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/different-vaccines\/Pfizer-BioNTech.html) advise that people do not get the Pfizer vaccine if they have had a severe or immediate allergic reaction to any ingredient in an mRNA COVID-19 vaccine, e.g., to polyethylene glycol (PEG) or polysorbate.\n\nThe CDC define an immediate allergic reaction as a reaction that takes place within 4 hours of exposure, causing symptoms such as:\n\n- [hives](https:\/\/www.medicalnewstoday.com\/articles\/157260)\n- swelling\n- wheezing or difficulty breathing\n\nPeople who have experienced allergic reactions to other vaccines should speak with a healthcare professional before getting a COVID-19 vaccine.\n\nPeople should also speak with a doctor before getting the Pfizer vaccine if they have:\n\n- other allergies\n- a [fever](https:\/\/www.medicalnewstoday.com\/articles\/168266)\n- a bleeding disorder or take medications to thin the blood\n- a compromised immune system or take medication that affects the immune system\n- are pregnant, planning to become pregnant, or are breastfeeding\n- have already received another COVID-19 vaccine\n\nWhen considering the impact of the Pfizer vaccine, it is important to distinguish between its efficacy and its effectiveness.\n\n“Efficacy” refers to the vaccine’s performance under ideal and controlled circumstances, such as in clinical trials. “Effectiveness” refers to its performance in real-world situations.\n\nEfficacy\n\nThere is strong evidence from clinical trials that the Pfizer vaccine has a high level of efficacy.\n\nA trial involving 43,548 participants, funded by BioNTech and Pfizer, reported that 2 doses of their vaccine confer [95% protection](https:\/\/www.nejm.org\/doi\/full\/10.1056\/NEJMoa2034577) against COVID-19 in people aged 16 years and older.\n\nEffectiveness\n\nThis result was consistent across age groups, sexes, races, ethnicities, and body weights, as well as those with underlying medical conditions and people who have already had a SARS-CoV-2 infection.\n\nA [large study](https:\/\/www.nejm.org\/doi\/full\/10.1056\/NEJMoa2101765) on the Pfizer vaccine involving about 1.2 million people in Israel supports the findings of clinical trials. It indicates that two doses of the vaccine reduce symptomatic cases of COVID-19 by 94% across all age groups after 7 days of receiving the second dose. The vaccine also reduces severe illness by 92%.\n\nWhat about new variants?\n\nIn some parts of the world, new variants of the SARS-CoV-2 virus have emerged. While concerning, this is normal because viruses evolve over time.\n\nIt is likely that the Pfizer vaccine will still be effective against current variants. A [preview of a paper](https:\/\/www.biorxiv.org\/content\/10.1101\/2021.01.07.425740v1) that looks at one particular mutation, present in variants first identified in the United Kingdom and South Africa, suggests that the Pfizer vaccine still works against them.\n\nResearch to date indicates that the Pfizer vaccine is safe for those who are eligible for it. Its manufacturers developed the vaccine according to international safety standards.\n\nThis vaccine has full authorization from the FDA and the European Medical Association.\n\nSome people may experience temporary side effects after receiving the Pfizer vaccine, which may last [a few days](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/expect\/after.html). These include:\n\n- pain and swelling around the injection site\n- chills\n- fever\n- a [headache](https:\/\/www.medicalnewstoday.com\/articles\/73936)\n- [tiredness](https:\/\/www.medicalnewstoday.com\/articles\/248002)\n\nUsually, these side effects indicate that the vaccine is working and are signs that the immune system is responding to it.\n\n- muscle pain\n- joint pain\n- nausea\n- swollen lymph nodes\n- allergic reactions\n\nSide effects are [more common](https:\/\/www.fda.gov\/emergency-preparedness-and-response\/coronavirus-disease-2019-covid-19\/pfizer-biontech-covid-19-vaccine) after the second dose than the first dose.\n\nIf a person experiences side effects after vaccination, they can take steps to care for themselves. Cool compresses and exercising the arm may ease pain and swelling while staying cool, and drinking fluids can help with a fever.\n\nPeople can also discuss trying over-the-counter (OTC) pain medications, such as acetaminophen, with a doctor or pharmacist.\n\nIn rare cases, people can experience a severe allergic reaction up to [60 minutes](https:\/\/www.ncbi.nlm.nih.gov\/pmc\/articles\/PMC7808711\/) after receiving the vaccine. Signs and symptoms include:\n\n- breathing difficulties\n- dizziness\n- rapid heartbeat\n- rash all over the body\n- swelling of the face and throat\n- weakness\n\nOther [rare side effects](https:\/\/www.fda.gov\/news-events\/press-announcements\/coronavirus-covid-19-update-june-25-2021) following vaccination can include myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the tissue surrounding the heart). These side effects are more likely following the second dose of the vaccine.\n\nIf a person experiences any of the above symptoms, dial 911 or call a local emergency department immediately.\n\nBased on how mRNA vaccines work, the [CDC](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/recommendations\/pregnancy.html) do not believe they pose a specific risk during pregnancy. However, there is currently limited evidence to confirm this.\n\n[Animal studies](https:\/\/www.acog.org\/covid-19\/covid-19-vaccines-and-pregnancy-conversation-guide-for-clinicians) on the effects of the Pfizer vaccine found no direct or indirect risks to pregnancy or the health of the fetus. Another mRNA vaccine by Moderna had similar results.\n\nIn February 2021, Pfizer and BioNTech announced they would begin human trials, testing their COVID-19 vaccine on [4,000](https:\/\/www.pfizer.com\/news\/press-release\/press-release-detail\/pfizer-and-biontech-commence-global-clinical-trial-evaluate) healthy pregnant adult females. These trials are still ongoing.\n\nIf someone is unsure whether they should get the Pfizer vaccine due to being pregnant, they can discuss their concerns with a doctor. Some may be more comfortable waiting for the results of human trials, while others may want to get a vaccine as soon as they can.\n\nCOVID-19 [does pose](https:\/\/www.acog.org\/covid-19\/covid-19-vaccines-and-pregnancy-conversation-guide-for-clinicians) an increased risk of severe illness during pregnancy.\n\nThe Moderna and Pfizer vaccines have similar efficacy rates in clinical trials and involve receiving two shots several weeks apart.\n\nThe table below outlines the differences:\n\n|   | **Pfizer** | **Moderna** |\n|---|---|---|\n| **Age** | [12 and up](https:\/\/www.cdc.gov\/vaccines\/covid-19\/info-by-product\/pfizer\/index.html) | [18 and up](https:\/\/www.cdc.gov\/vaccines\/covid-19\/info-by-product\/moderna\/index.html) |\n| **Dosage** | two shots, 21 days apart | two shots, 28 days apart |\n| **Efficacy** | [95%](https:\/\/www.nejm.org\/doi\/full\/10.1056\/NEJMoa2034577) after two doses | [92%](https:\/\/www.who.int\/news-room\/feature-stories\/detail\/the-moderna-covid-19-mrna-1273-vaccine-what-you-need-to-know) 14 days after the first dose |\n| **Storage** | In an ultra-cold freezer at -112°F to -76°F (-80°C to -60°C), or at –[25°C to -15°C (-13°F to 5°F)](https:\/\/www.fda.gov\/media\/144413\/download) for up to 2 weeks | In a freezer between -13° F and 5°F, or in the refrigerator between 36°F and 46°F (2°C and 8°C) for up to 30 days |\n\nLarge-scale clinical trials are underway for two other COVID-19 vaccines from:\n\n- AstraZeneca\n- Novavax\n\nThe AstraZeneca vaccination has an efficacy of [63\\.09%](https:\/\/www.who.int\/news-room\/feature-stories\/detail\/the-oxford-astrazeneca-covid-19-vaccine-what-you-need-to-know) against symptomatic COVID-19. It requires two doses, given 8–12 weeks apart. A longer interval in between doses has associations with greater efficacy.\n\nNovavax reported that their COVID-19 vaccine candidate shows [89\\.3%](https:\/\/ir.novavax.com\/news-releases\/news-release-details\/novavax-covid-19-vaccine-demonstrates-893-efficacy-uk-phase-3) efficacy in U.K. phase three trials. Research indicates that the vaccine efficacy might be [86%](https:\/\/www.bmj.com\/content\/372\/bmj.n296) against the variant first identified in the U.K., and 60% against the variant first identified in South Africa.\n\nThe main benefit of getting a COVID-19 vaccine is protection from the disease, its symptoms, and its complications.\n\nCOVID-19 has a wide range of effects on the body. For some, it is a mild short-term illness. For others, it is severe and can be life threatening. Some people also go on to experience [long COVID](https:\/\/www.medicalnewstoday.com\/articles\/long-term-effects-of-coronavirus), which can last for weeks or months.\n\nPeople who have received a vaccine may also be [less likely](https:\/\/www.who.int\/news-room\/q-a-detail\/coronavirus-disease-\\(covid-19\\)-vaccines) to transmit the virus that causes the COVID-19 to other people, reducing the risk of others getting sick, particularly vulnerable people.\n\nMass vaccination may also allow people to see their friends and family or go back to work sooner. However, no COVID-19 vaccine is 100% effective, so there is still some risk for those who receive a vaccine. Additionally, at present, scientists are unclear how long protection from vaccines lasts.\n\nEven if a person has received two doses, they [still need](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/faq.html) to follow safety guidelines for their local area, such as:\n\n- physical distancing\n- hand washing\n- wearing a mask\n\nGetting a vaccine is not compulsory. However, people who do not get a vaccine are at increased risk of developing COVID-19 than those who receive one.\n\nSome people are unable to get a COVID-19 vaccine for health reasons. Other people may choose not to.\n\nThe [FDA](https:\/\/www.fda.gov\/media\/144638\/download) state that it is an individual choice as to whether someone does or does not receive a COVID-19 vaccine. Choosing not to receive a vaccine will not impact their standard of medical care in the U.S.\n\nPeople who do not get a vaccine should take care to follow safety guidelines to reduce the risk.\n\nThe Pfizer vaccine for the novel coronavirus, SARS-CoV-2, appears to be effective in clinical trials and real-world situations. Current evidence shows it is safe for most adults.\n\nCommon side effects include chills, fever, tiredness, headache, and pain or swelling at the injection site. This should only last a few days.\n\nPeople can discuss different vaccines and their safety with a healthcare professional. People still need to wear masks, practice physical distancing, and follow hygiene guidelines to prevent transmission until advised otherwise.\n\n***For live updates on the latest developments regarding the novel [coronavirus](https:\/\/www.medicalnewstoday.com\/articles\/256521) and COVID-19, click [here](https:\/\/www.medicalnewstoday.com\/articles\/live-updates-coronavirus-covid-19)***.","meta_canonical":null}

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Boilerpipe Text	The Pfizer-BioNTech vaccine is one of several vaccines that can protect against COVID-19. Research indicates that the vaccine has high efficacy in people aged 16 and over. The Pfizer vaccine for COVID-19 is available in the United States and other countries. Side effects are typically mild and last a few days . Read on to learn more about the Pfizer vaccine, including how it works, ingredients, effectiveness, and safety. The Pfizer vaccine is a shot that may protect people from developing COVID-19. Its brand name is Comirnaty. Pfizer Inc., one of the world’s largest biopharmaceutical companies, and BioNTech, a German biotechnology company, created this vaccine. According to the Centers for Disease Control and Prevention (CDC), people receive this vaccine in two doses, with the second dose coming about 21 days after the first. However, sometimes, a person may not receive the second dose until 6 weeks after the first. The vaccine works by introducing a molecule to cells, known as messenger RNA (mRNA). This molecule teaches cells to make a protein from the virus that causes COVID-19, which is SARS-CoV-2. The body detects this protein and triggers an immune response. This creates antibodies, as well as longer lasting immunity that can fight off future SARS-CoV-2 infections. mRNA lipids ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide, 1,2-Distearoyl-sn-glycero-3-phosphocholine, and cholesterol) monobasic potassium phosphate and dibasic sodium phosphate dehydrate, which act as buffers potassium chloride and sodium chloride, which are types of salt sucrose, or table sugar It does not contain allergens, such as eggs, latex, or preservatives. The FDA has authorized the use of the Pfizer vaccine to prevent COVID-19 in people aged 12 years of age and older . Most adults will be eligible for this vaccine. However, some may need to avoid it for safety reasons. The Centers for Disease Control and Prevention (CDC) advise that people do not get the Pfizer vaccine if they have had a severe or immediate allergic reaction to any ingredient in an mRNA COVID-19 vaccine, e.g., to polyethylene glycol (PEG) or polysorbate. The CDC define an immediate allergic reaction as a reaction that takes place within 4 hours of exposure, causing symptoms such as: hives swelling wheezing or difficulty breathing People who have experienced allergic reactions to other vaccines should speak with a healthcare professional before getting a COVID-19 vaccine. People should also speak with a doctor before getting the Pfizer vaccine if they have: other allergies a fever a bleeding disorder or take medications to thin the blood a compromised immune system or take medication that affects the immune system are pregnant, planning to become pregnant, or are breastfeeding have already received another COVID-19 vaccine When considering the impact of the Pfizer vaccine, it is important to distinguish between its efficacy and its effectiveness. “Efficacy” refers to the vaccine’s performance under ideal and controlled circumstances, such as in clinical trials. “Effectiveness” refers to its performance in real-world situations. Efficacy There is strong evidence from clinical trials that the Pfizer vaccine has a high level of efficacy. A trial involving 43,548 participants, funded by BioNTech and Pfizer, reported that 2 doses of their vaccine confer 95% protection against COVID-19 in people aged 16 years and older. Effectiveness This result was consistent across age groups, sexes, races, ethnicities, and body weights, as well as those with underlying medical conditions and people who have already had a SARS-CoV-2 infection. A large study on the Pfizer vaccine involving about 1.2 million people in Israel supports the findings of clinical trials. It indicates that two doses of the vaccine reduce symptomatic cases of COVID-19 by 94% across all age groups after 7 days of receiving the second dose. The vaccine also reduces severe illness by 92%. What about new variants? In some parts of the world, new variants of the SARS-CoV-2 virus have emerged. While concerning, this is normal because viruses evolve over time. It is likely that the Pfizer vaccine will still be effective against current variants. A preview of a paper that looks at one particular mutation, present in variants first identified in the United Kingdom and South Africa, suggests that the Pfizer vaccine still works against them. Research to date indicates that the Pfizer vaccine is safe for those who are eligible for it. Its manufacturers developed the vaccine according to international safety standards. This vaccine has full authorization from the FDA and the European Medical Association. Some people may experience temporary side effects after receiving the Pfizer vaccine, which may last a few days . These include: pain and swelling around the injection site chills fever a headache tiredness Usually, these side effects indicate that the vaccine is working and are signs that the immune system is responding to it. muscle pain joint pain nausea swollen lymph nodes allergic reactions Side effects are more common after the second dose than the first dose. If a person experiences side effects after vaccination, they can take steps to care for themselves. Cool compresses and exercising the arm may ease pain and swelling while staying cool, and drinking fluids can help with a fever. People can also discuss trying over-the-counter (OTC) pain medications, such as acetaminophen, with a doctor or pharmacist. In rare cases, people can experience a severe allergic reaction up to 60 minutes after receiving the vaccine. Signs and symptoms include: breathing difficulties dizziness rapid heartbeat rash all over the body swelling of the face and throat weakness Other rare side effects following vaccination can include myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the tissue surrounding the heart). These side effects are more likely following the second dose of the vaccine. If a person experiences any of the above symptoms, dial 911 or call a local emergency department immediately. Based on how mRNA vaccines work, the CDC do not believe they pose a specific risk during pregnancy. However, there is currently limited evidence to confirm this. Animal studies on the effects of the Pfizer vaccine found no direct or indirect risks to pregnancy or the health of the fetus. Another mRNA vaccine by Moderna had similar results. In February 2021, Pfizer and BioNTech announced they would begin human trials, testing their COVID-19 vaccine on 4,000 healthy pregnant adult females. These trials are still ongoing. If someone is unsure whether they should get the Pfizer vaccine due to being pregnant, they can discuss their concerns with a doctor. Some may be more comfortable waiting for the results of human trials, while others may want to get a vaccine as soon as they can. COVID-19 does pose an increased risk of severe illness during pregnancy. The Moderna and Pfizer vaccines have similar efficacy rates in clinical trials and involve receiving two shots several weeks apart. The table below outlines the differences: Pfizer Moderna Age 12 and up 18 and up Dosage two shots, 21 days apart two shots, 28 days apart Efficacy 95% after two doses 92% 14 days after the first dose Storage In an ultra-cold freezer at -112°F to -76°F (-80°C to -60°C), or at – 25°C to -15°C (-13°F to 5°F) for up to 2 weeks In a freezer between -13° F and 5°F, or in the refrigerator between 36°F and 46°F (2°C and 8°C) for up to 30 days Large-scale clinical trials are underway for two other COVID-19 vaccines from: AstraZeneca Novavax The AstraZeneca vaccination has an efficacy of 63.09% against symptomatic COVID-19. It requires two doses, given 8–12 weeks apart. A longer interval in between doses has associations with greater efficacy. Novavax reported that their COVID-19 vaccine candidate shows 89.3% efficacy in U.K. phase three trials. Research indicates that the vaccine efficacy might be 86% against the variant first identified in the U.K., and 60% against the variant first identified in South Africa. The main benefit of getting a COVID-19 vaccine is protection from the disease, its symptoms, and its complications. COVID-19 has a wide range of effects on the body. For some, it is a mild short-term illness. For others, it is severe and can be life threatening. Some people also go on to experience long COVID , which can last for weeks or months. People who have received a vaccine may also be less likely to transmit the virus that causes the COVID-19 to other people, reducing the risk of others getting sick, particularly vulnerable people. Mass vaccination may also allow people to see their friends and family or go back to work sooner. However, no COVID-19 vaccine is 100% effective, so there is still some risk for those who receive a vaccine. Additionally, at present, scientists are unclear how long protection from vaccines lasts. Even if a person has received two doses, they still need to follow safety guidelines for their local area, such as: physical distancing hand washing wearing a mask Getting a vaccine is not compulsory. However, people who do not get a vaccine are at increased risk of developing COVID-19 than those who receive one. Some people are unable to get a COVID-19 vaccine for health reasons. Other people may choose not to. The FDA state that it is an individual choice as to whether someone does or does not receive a COVID-19 vaccine. Choosing not to receive a vaccine will not impact their standard of medical care in the U.S. People who do not get a vaccine should take care to follow safety guidelines to reduce the risk. The Pfizer vaccine for the novel coronavirus, SARS-CoV-2, appears to be effective in clinical trials and real-world situations. Current evidence shows it is safe for most adults. Common side effects include chills, fever, tiredness, headache, and pain or swelling at the injection site. This should only last a few days. People can discuss different vaccines and their safety with a healthcare professional. People still need to wear masks, practice physical distancing, and follow hygiene guidelines to prevent transmission until advised otherwise. For live updates on the latest developments regarding the novel coronavirus and COVID-19, click here .
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[Bezzy Psoriasis](https://www.bezzypsoriasis.com/?utm_source=mnt&utm_medium=nav-bar-connect) Follow Us Subscribe # The Pfizer vaccine for coronavirus ![](https://i0.wp.com/post.medicalnewstoday.com/wp-content/uploads/2022/01/Alan-Carter-500x500-Bio.png?w=105&h=105) [Medically reviewed]() by [Alan Carter, Pharm.D.]() — Written by [Jayne Leonard]() — [Updated on June 28, 2021]() - [What it is](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#what-it-is) - [How it works](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#how-it-works) - [Ingredients](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#ingredients) - [Who is eligible?](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#who-is-eligible) - [Efficacy](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#efficacy) - [Safety](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#safety) - [Side effects](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#side-effects) - [Pregnancy](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#pregnancy) - [Vs. Moderna](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#vs-moderna) - [Wider impact](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#wider-impact) - [Not having a vaccine](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#not-having-a-vaccine) - [Summary](https://www.medicalnewstoday.com/articles/pfizer-vaccine-for-coronavirus#summary) The Pfizer-BioNTech vaccine is one of several vaccines that can protect against COVID-19. Research indicates that the vaccine has high efficacy in people aged 16 and over. This comes from the [New England Journal of Medicine](https://www.nejm.org/doi/full/10.1056/NEJMoa2034577). The Pfizer vaccine for COVID-19 is available in the United States and other countries. Side effects are typically mild and last [a few days](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html). Read on to learn more about the Pfizer vaccine, including how it works, ingredients, effectiveness, and safety. ### Coronavirus resources For more advice on COVID-19 prevention and treatment, visit our [coronavirus hub](https://www.medicalnewstoday.com/coronavirus). ## [What is the Pfizer vaccine?]() ![The silhouette of a hand holding a needle of the Pfizer vaccine, against a backdrop with the Pfizer logo printed across it.](https://i0.wp.com/post.medicalnewstoday.com/wp-content/uploads/sites/3/2021/02/Pfizer_vaccine_GettyImages1231469367_Header-1024x575.jpg?w=1155&h=1528) [Share on Pinterest](https://www.pinterest.com/pin/create/button/?url=https%3A%2F%2Fwww.medicalnewstoday.com%2Farticles%2Fpfizer-vaccine-for-coronavirus&media=https%3A%2F%2Fpost.medicalnewstoday.com%2Fwp-content%2Fuploads%2Fsites%2F3%2F2021%2F02%2FPfizer_vaccine_GettyImages1231469367_Header-1024x575.jpg&description=Pfizer%20vaccine%20for%20coronavirus%3A%20Efficacy%2C%20side%20effects%2C%20and%20more "Share on Pinterest") Jaap Arriens/NurPhoto via Getty Images The Pfizer vaccine is a shot that may protect people from developing COVID-19. Its brand name is Comirnaty. Pfizer Inc., one of the world’s largest biopharmaceutical companies, and BioNTech, a German biotechnology company, created this vaccine. According to the Centers for Disease Control and Prevention (CDC), people receive this vaccine in two doses, with the second dose coming about [21 days](https://www.cdc.gov/vaccines/covid-19/info-by-product/pfizer/index.html) after the first. However, sometimes, a person may not receive the second dose until 6 weeks after the first. ## [How does the Pfizer vaccine work?]() The vaccine works by introducing a molecule to cells, known as messenger RNA (mRNA). This molecule teaches cells to make a protein from the virus that causes COVID-19, which is SARS-CoV-2. The body detects this protein and triggers an immune response. This creates antibodies, as well as longer lasting immunity that can fight off future SARS-CoV-2 infections. [Learn more about how mRNA vaccines work.](https://www.medicalnewstoday.com/articles/what-is-a-vaccine) ## [What does the vaccine contain?]() The [Food and Drug Administration (FDA)](https://www.fda.gov/media/144414/download) state that the Pfizer vaccine contains: - mRNA - lipids ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2\[(polyethylene glycol)-2000\]-N,N-ditetradecylacetamide, 1,2-Distearoyl-sn-glycero-3-phosphocholine, and cholesterol) - monobasic potassium phosphate and dibasic sodium phosphate dehydrate, which act as buffers - potassium chloride and sodium chloride, which are types of salt - sucrose, or table sugar It does not contain allergens, such as eggs, latex, or preservatives. [Learn more about allergies and allergens here.](https://www.medicalnewstoday.com/articles/264419) ## [Who can have the Pfizer vaccine?]() The FDA has authorized the use of the Pfizer vaccine to prevent COVID-19 in people aged [12 years of age and older](https://www.fda.gov/media/144414/download). Most adults will be eligible for this vaccine. However, some may need to avoid it for safety reasons. The [Centers for Disease Control and Prevention (CDC)](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/Pfizer-BioNTech.html) advise that people do not get the Pfizer vaccine if they have had a severe or immediate allergic reaction to any ingredient in an mRNA COVID-19 vaccine, e.g., to polyethylene glycol (PEG) or polysorbate. The CDC define an immediate allergic reaction as a reaction that takes place within 4 hours of exposure, causing symptoms such as: - [hives](https://www.medicalnewstoday.com/articles/157260) - swelling - wheezing or difficulty breathing People who have experienced allergic reactions to other vaccines should speak with a healthcare professional before getting a COVID-19 vaccine. People should also speak with a doctor before getting the Pfizer vaccine if they have: - other allergies - a [fever](https://www.medicalnewstoday.com/articles/168266) - a bleeding disorder or take medications to thin the blood - a compromised immune system or take medication that affects the immune system - are pregnant, planning to become pregnant, or are breastfeeding - have already received another COVID-19 vaccine [Learn more about getting the COVID-19 vaccination here.](http://articles/coronavirus-vaccine) ## [How effective is the Pfizer vaccine?]() When considering the impact of the Pfizer vaccine, it is important to distinguish between its efficacy and its effectiveness. “Efficacy” refers to the vaccine’s performance under ideal and controlled circumstances, such as in clinical trials. “Effectiveness” refers to its performance in real-world situations. ### Efficacy There is strong evidence from clinical trials that the Pfizer vaccine has a high level of efficacy. A trial involving 43,548 participants, funded by BioNTech and Pfizer, reported that 2 doses of their vaccine confer [95% protection](https://www.nejm.org/doi/full/10.1056/NEJMoa2034577) against COVID-19 in people aged 16 years and older. ### Effectiveness This result was consistent across age groups, sexes, races, ethnicities, and body weights, as well as those with underlying medical conditions and people who have already had a SARS-CoV-2 infection. A [large study](https://www.nejm.org/doi/full/10.1056/NEJMoa2101765) on the Pfizer vaccine involving about 1.2 million people in Israel supports the findings of clinical trials. It indicates that two doses of the vaccine reduce symptomatic cases of COVID-19 by 94% across all age groups after 7 days of receiving the second dose. The vaccine also reduces severe illness by 92%. ### What about new variants? In some parts of the world, new variants of the SARS-CoV-2 virus have emerged. While concerning, this is normal because viruses evolve over time. It is likely that the Pfizer vaccine will still be effective against current variants. A [preview of a paper](https://www.biorxiv.org/content/10.1101/2021.01.07.425740v1) that looks at one particular mutation, present in variants first identified in the United Kingdom and South Africa, suggests that the Pfizer vaccine still works against them. [Find out more about vaccines and how they work here.](https://www.medicalnewstoday.com/articles/what-is-a-vaccine) ## [Safety]() Research to date indicates that the Pfizer vaccine is safe for those who are eligible for it. Its manufacturers developed the vaccine according to international safety standards. This vaccine has full authorization from the FDA and the European Medical Association. ## [Side effects]() Some people may experience temporary side effects after receiving the Pfizer vaccine, which may last [a few days](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html). These include: - pain and swelling around the injection site - chills - fever - a [headache](https://www.medicalnewstoday.com/articles/73936) - [tiredness](https://www.medicalnewstoday.com/articles/248002) Usually, these side effects indicate that the vaccine is working and are signs that the immune system is responding to it. [Less commonly](https://www.fda.gov/media/144414/download), people experience: - muscle pain - joint pain - nausea - swollen lymph nodes - allergic reactions Side effects are [more common](https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/pfizer-biontech-covid-19-vaccine) after the second dose than the first dose. If a person experiences side effects after vaccination, they can take steps to care for themselves. Cool compresses and exercising the arm may ease pain and swelling while staying cool, and drinking fluids can help with a fever. People can also discuss trying over-the-counter (OTC) pain medications, such as acetaminophen, with a doctor or pharmacist. In rare cases, people can experience a severe allergic reaction up to [60 minutes](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7808711/) after receiving the vaccine. Signs and symptoms include: - breathing difficulties - dizziness - rapid heartbeat - rash all over the body - swelling of the face and throat - weakness Other [rare side effects](https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-june-25-2021) following vaccination can include myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the tissue surrounding the heart). These side effects are more likely following the second dose of the vaccine. If a person experiences any of the above symptoms, dial 911 or call a local emergency department immediately. [Learn more about the safety and other facts about COVID-19 vaccinations here.](https://www.medicalnewstoday.com/articles/coronavirus-vaccine) ## [Safety during pregnancy]() Based on how mRNA vaccines work, the [CDC](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/pregnancy.html) do not believe they pose a specific risk during pregnancy. However, there is currently limited evidence to confirm this. [Animal studies](https://www.acog.org/covid-19/covid-19-vaccines-and-pregnancy-conversation-guide-for-clinicians) on the effects of the Pfizer vaccine found no direct or indirect risks to pregnancy or the health of the fetus. Another mRNA vaccine by Moderna had similar results. In February 2021, Pfizer and BioNTech announced they would begin human trials, testing their COVID-19 vaccine on [4,000](https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-commence-global-clinical-trial-evaluate) healthy pregnant adult females. These trials are still ongoing. If someone is unsure whether they should get the Pfizer vaccine due to being pregnant, they can discuss their concerns with a doctor. Some may be more comfortable waiting for the results of human trials, while others may want to get a vaccine as soon as they can. COVID-19 [does pose](https://www.acog.org/covid-19/covid-19-vaccines-and-pregnancy-conversation-guide-for-clinicians) an increased risk of severe illness during pregnancy. [Learn more about how COVID-19 affects pregnancy here.](https://www.medicalnewstoday.com/articles/covid-19-during-pregnancy-how-the-placenta-is-involved) ## [Comparison to the Moderna vaccine]() The Moderna and Pfizer vaccines have similar efficacy rates in clinical trials and involve receiving two shots several weeks apart. The table below outlines the differences: \| \| Pfizer \| Moderna \| \|---\|---\|---\| \| Age \| [12 and up](https://www.cdc.gov/vaccines/covid-19/info-by-product/pfizer/index.html) \| [18 and up](https://www.cdc.gov/vaccines/covid-19/info-by-product/moderna/index.html) \| \| Dosage \| two shots, 21 days apart \| two shots, 28 days apart \| \| Efficacy \| [95%](https://www.nejm.org/doi/full/10.1056/NEJMoa2034577) after two doses \| [92%](https://www.who.int/news-room/feature-stories/detail/the-moderna-covid-19-mrna-1273-vaccine-what-you-need-to-know) 14 days after the first dose \| \| Storage \| In an ultra-cold freezer at -112°F to -76°F (-80°C to -60°C), or at –[25°C to -15°C (-13°F to 5°F)](https://www.fda.gov/media/144413/download) for up to 2 weeks \| In a freezer between -13° F and 5°F, or in the refrigerator between 36°F and 46°F (2°C and 8°C) for up to 30 days \| Large-scale clinical trials are underway for two other COVID-19 vaccines from: - AstraZeneca - Novavax The AstraZeneca vaccination has an efficacy of [63\.09%](https://www.who.int/news-room/feature-stories/detail/the-oxford-astrazeneca-covid-19-vaccine-what-you-need-to-know) against symptomatic COVID-19. It requires two doses, given 8–12 weeks apart. A longer interval in between doses has associations with greater efficacy. Novavax reported that their COVID-19 vaccine candidate shows [89\.3%](https://ir.novavax.com/news-releases/news-release-details/novavax-covid-19-vaccine-demonstrates-893-efficacy-uk-phase-3) efficacy in U.K. phase three trials. Research indicates that the vaccine efficacy might be [86%](https://www.bmj.com/content/372/bmj.n296) against the variant first identified in the U.K., and 60% against the variant first identified in South Africa. [Learn more about the Moderna vaccine here](https://www.medicalnewstoday.com/articles/moderna-vaccine-for-coronavirus). ## [Impact]() The main benefit of getting a COVID-19 vaccine is protection from the disease, its symptoms, and its complications. COVID-19 has a wide range of effects on the body. For some, it is a mild short-term illness. For others, it is severe and can be life threatening. Some people also go on to experience [long COVID](https://www.medicalnewstoday.com/articles/long-term-effects-of-coronavirus), which can last for weeks or months. People who have received a vaccine may also be [less likely](https://www.who.int/news-room/q-a-detail/coronavirus-disease-\(covid-19\)-vaccines) to transmit the virus that causes the COVID-19 to other people, reducing the risk of others getting sick, particularly vulnerable people. Mass vaccination may also allow people to see their friends and family or go back to work sooner. However, no COVID-19 vaccine is 100% effective, so there is still some risk for those who receive a vaccine. Additionally, at present, scientists are unclear how long protection from vaccines lasts. Even if a person has received two doses, they [still need](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/faq.html) to follow safety guidelines for their local area, such as: - physical distancing - hand washing - wearing a mask [Learn more tips for preventing the spread of SARS-CoV-2.](https://www.medicalnewstoday.com/articles/coronavirus-prevention) ## [What happens if you do not get a vaccine?]() Getting a vaccine is not compulsory. However, people who do not get a vaccine are at increased risk of developing COVID-19 than those who receive one. Some people are unable to get a COVID-19 vaccine for health reasons. Other people may choose not to. The [FDA](https://www.fda.gov/media/144638/download) state that it is an individual choice as to whether someone does or does not receive a COVID-19 vaccine. Choosing not to receive a vaccine will not impact their standard of medical care in the U.S. People who do not get a vaccine should take care to follow safety guidelines to reduce the risk. ## [Summary]() The Pfizer vaccine for the novel coronavirus, SARS-CoV-2, appears to be effective in clinical trials and real-world situations. Current evidence shows it is safe for most adults. Common side effects include chills, fever, tiredness, headache, and pain or swelling at the injection site. This should only last a few days. People can discuss different vaccines and their safety with a healthcare professional. People still need to wear masks, practice physical distancing, and follow hygiene guidelines to prevent transmission until advised otherwise. *For live updates on the latest developments regarding the novel [coronavirus](https://www.medicalnewstoday.com/articles/256521) and COVID-19, click [here](https://www.medicalnewstoday.com/articles/live-updates-coronavirus-covid-19). - [Flu / Cold / SARS](https://www.medicalnewstoday.com/categories/flu-sars) - [Immune System / Vaccines](https://www.medicalnewstoday.com/categories/immune-system) - [Infectious Diseases / Bacteria / Viruses](https://www.medicalnewstoday.com/categories/infectious_diseases) - [COVID-19](https://www.medicalnewstoday.com/categories/covid-19) - [Cat 1](https://www.medicalnewstoday.com/categories/cat1-en) ### How we reviewed this article: Sources Medical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our [editorial policy](https://www.medicalnewstoday.com/articles/process). - Allergic reactions including anaphylaxis after receipt of the first dose of Pfizer-BioNTech COVID-19 vaccine. (2021). <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7808711/> - Coronavirus (COVID-19) update: FDA Allows more flexible storage, transportation conditions for Pfizer-BioNTech COVID-19 vaccine. (2021). <https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-allows-more-flexible-storage-transportation-conditions-pfizer> - Coronavirus (COVID-19) update: FDA limits use of Janssen COVID-19 vaccine to certain individuals. (2022). <https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-limits-use-janssen-covid-19-vaccine-certain-individuals> - Coronavirus disease (COVID-19): Vaccines. (2020). <https://www.who.int/news-room/q-a-detail/coronavirus-disease-(covid-19)-vaccines> - Coronavirus (COVID-19) update: June 25, 2021. (2021). <https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-june-25-2021> - COVID-19 vaccines and pregnancy: Conversation guide for clinicians. (n.d.). <https://www.acog.org/covid-19/covid-19-vaccines-and-pregnancy-conversation-guide-for-clinicians> - Dagan, N., et al.* (2021). BNT162b2 mRNA Covid-19 vaccine in a nationwide mass vaccination setting. <https://www.nejm.org/doi/full/10.1056/NEJMoa2101765> - Different COVID-19 vaccines. (2021). <https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines.html> - EMA recommends first COVID-19 vaccine for authorisation in the EU. (2020). <https://www.ema.europa.eu/en/news/ema-recommends-first-covid-19-vaccine-authorisation-eu> - Fact sheet for healthcare providers administering vaccination (vaccination providers). Emergency use authorization (EUA) of the Pfizer-Biontech COVID-19 vaccine to prevent coronavirus disease 2019 (COVID-19) \[Fact sheet\]. (2021). <https://www.fda.gov/media/144413/download> - Fact sheet for recipients and caregivers. Emergency use authorization (EUA) of the Moderna COVID-19 vaccine to prevent coronavirus disease 2019 (COVID-19) in individuals 18 years of age and older. (2020). <https://www.fda.gov/media/144638/download> - FDA briefing document: Moderna COVID-19 vaccine. (2020). <https://www.fda.gov/media/144434/download> - Frequently asked questions about COVID-19 vaccination. (2021). <https://www.cdc.gov/coronavirus/2019-ncov/vaccines/faq.html> - Information about the Pfizer-BioNTech COVID-19 vaccine. (2021). <https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/Pfizer-BioNTech.html> - Janssen COVID-19 vaccine. (2022). <https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/janssen-covid-19-vaccine> - Johnson & Johnson announces single-shot Janssen COVID-19 vaccine candidate met primary endpoints in interim analysis of its phase 3 ENSEMBLE trial. (2021). <https://www.jnj.com/johnson-johnson-announces-single-shot-janssen-covid-19-vaccine-candidate-met-primary-endpoints-in-interim-analysis-of-its-phase-3-ensemble-trial> - Johnson & Johnson. (2021). Johnson & Johnson COVID-19 vaccine authorized by U.S. FDA for emergency use – first single-shot vaccine in fight against global pandemic \[Press release\]. <https://www.jnj.com/johnson-johnson-covid-19-vaccine-authorized-by-u-s-fda-for-emergency-usefirst-single-shot-vaccine-in-fight-against-global-pandemic> - Mahase, E. (2021). COVID-19: Assess the effects of extending Pfizer vaccine dosing interval, expert urges. <https://www.bmj.com/content/372/bmj.n162> - Mahase, E. (2021). COVID-19: Novavax vaccine efficacy is 86% against UK variant and 60% against South African variant. <https://www.bmj.com/content/372/bmj.n296> - Mahase, E. (2020). Covid-19: Pfizer vaccine efficacy was 52% after first dose and 95% after second dose, paper shows. <https://www.bmj.com/content/371/bmj.m4826> - Mahase, E. (2021). COVID-19: Reports from Israel suggest one dose of Pfizer vaccine could be less effective than expected. <https://www.bmj.com/content/372/bmj.n217> - Moderna COVID-19 vaccine. (2021). <https://www.cdc.gov/vaccines/covid-19/info-by-product/moderna/index.html> - Novavax. (2021). Novavax COVID-19 vaccine demonstrates 89.3% efficacy in UK phase 3 tria \[Press release\]. <https://ir.novavax.com/news-releases/news-release-details/novavax-covid-19-vaccine-demonstrates-893-efficacy-uk-phase-3> - Pfizer. (2021). Pfizer and BioNTech commence global clinical trial to evaluate COVID-19 vaccine in pregnant women \[Press release\]. <https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-commence-global-clinical-trial-evaluate> - Pfizer-BioNTech COVID-19 vaccine. (2021). <https://www.cdc.gov/vaccines/covid-19/info-by-product/pfizer/index.html> - Pfizer-BioNTech COVID-19 vaccine. (2021). <https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/pfizer-biontech-covid-19-vaccine> - Pfizer-BioNTech COVID-19 Vaccine EUA fact sheet for recipients and caregivers. (2021). <https://www.fda.gov/media/144414/download> - Polack, F. P., et al. (2020). Safety and efficacy of the BNT162b2 mRNA Covid-19 vaccine. <https://www.nejm.org/doi/full/10.1056/NEJMoa2034577> - Possible side effects after getting a COVID-19 vaccine (2021). <https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html> - Singal, A. G., et al. (2014). A primer on effectiveness and efficacy trials. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3912314/> - The Advisory Committee on Immunization Practices’ interim recommendation for use of Pfizer-BioNTech COVID-19 vaccine. (2020). <https://www.cdc.gov/mmwr/volumes/69/wr/mm6950e2.htm> - The Moderna COVID-19 (mRNA-1273) vaccine: What you need to know. (2021). <https://www.who.int/news-room/feature-stories/detail/the-moderna-covid-19-mrna-1273-vaccine-what-you-need-to-know> - The Oxford/AstraZeneca COVID-19 vaccine: What you need to know. (2021). <https://www.who.int/news-room/feature-stories/detail/the-oxford-astrazeneca-covid-19-vaccine-what-you-need-to-know> - Understanding mRNA COVID-19 vaccines. (2020). <https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html> - Vaccination considerations for people who are pregnant or breastfeeding. (2021). <https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/pregnancy.html> - Xie, X., et al. (2021). Neutralization of N501Y mutant SARS-CoV-2 by BNT162b2 vaccine-elicited sera. <https://www.biorxiv.org/content/10.1101/2021.01.07.425740v1> Share this article ![](https://i0.wp.com/post.medicalnewstoday.com/wp-content/uploads/2022/01/Alan-Carter-500x500-Bio.png?w=105&h=105) [Medically reviewed]() by [Alan Carter, Pharm.D.]() — Written by [Jayne Leonard]() — [Updated on June 28, 2021]() ## Latest news - [Could probiotics, dietary changes help protect brain health as we age?](https://www.medicalnewstoday.com/articles/could-probiotics-dietary-changes-help-protect-brain-health-as-we-age) - [9 steps to improve heart health, per new dietary guidance from AHA](https://www.medicalnewstoday.com/articles/9-steps-improve-heart-health-diet-guidance-aha) - [AI model can accurately predict liver cancer risk, study suggests](https://www.medicalnewstoday.com/articles/ai-model-accurately-predict-liver-cancer-risk) - [AI-powered stroke tool linked to improved patient outcomes in large clinical trial](https://www.medicalnewstoday.com/articles/ai-powered-stroke-tool-linked-improved-patient-outcomes-large-clinical-trial) - [Eating same meals on repeat, and more at weekends may help you lose more weight](https://www.medicalnewstoday.com/articles/eating-same-meals-repeat-more-weekends-may-help-lose-more-weight) ### Related Coverage - [Coronavirus (COVID-19) vaccine: What to know](https://www.medicalnewstoday.com/articles/coronavirus-vaccine?utm_source=ReadNext) Medically reviewed by [Avi Varma, MD, MPH, AAHIVS, FAAFP](https://www.medicalnewstoday.com/reviewers) [COVID-19 vaccines help prevent illness, particularly in vulnerable groups. 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Readable Markdown	The Pfizer-BioNTech vaccine is one of several vaccines that can protect against COVID-19. Research indicates that the vaccine has high efficacy in people aged 16 and over. The Pfizer vaccine for COVID-19 is available in the United States and other countries. Side effects are typically mild and last [a few days](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html). Read on to learn more about the Pfizer vaccine, including how it works, ingredients, effectiveness, and safety. The Pfizer vaccine is a shot that may protect people from developing COVID-19. Its brand name is Comirnaty. Pfizer Inc., one of the world’s largest biopharmaceutical companies, and BioNTech, a German biotechnology company, created this vaccine. According to the Centers for Disease Control and Prevention (CDC), people receive this vaccine in two doses, with the second dose coming about [21 days](https://www.cdc.gov/vaccines/covid-19/info-by-product/pfizer/index.html) after the first. However, sometimes, a person may not receive the second dose until 6 weeks after the first. The vaccine works by introducing a molecule to cells, known as messenger RNA (mRNA). This molecule teaches cells to make a protein from the virus that causes COVID-19, which is SARS-CoV-2. The body detects this protein and triggers an immune response. This creates antibodies, as well as longer lasting immunity that can fight off future SARS-CoV-2 infections. - mRNA - lipids ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2\[(polyethylene glycol)-2000\]-N,N-ditetradecylacetamide, 1,2-Distearoyl-sn-glycero-3-phosphocholine, and cholesterol) - monobasic potassium phosphate and dibasic sodium phosphate dehydrate, which act as buffers - potassium chloride and sodium chloride, which are types of salt - sucrose, or table sugar It does not contain allergens, such as eggs, latex, or preservatives. The FDA has authorized the use of the Pfizer vaccine to prevent COVID-19 in people aged [12 years of age and older](https://www.fda.gov/media/144414/download). Most adults will be eligible for this vaccine. However, some may need to avoid it for safety reasons. The [Centers for Disease Control and Prevention (CDC)](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/Pfizer-BioNTech.html) advise that people do not get the Pfizer vaccine if they have had a severe or immediate allergic reaction to any ingredient in an mRNA COVID-19 vaccine, e.g., to polyethylene glycol (PEG) or polysorbate. The CDC define an immediate allergic reaction as a reaction that takes place within 4 hours of exposure, causing symptoms such as: - [hives](https://www.medicalnewstoday.com/articles/157260) - swelling - wheezing or difficulty breathing People who have experienced allergic reactions to other vaccines should speak with a healthcare professional before getting a COVID-19 vaccine. People should also speak with a doctor before getting the Pfizer vaccine if they have: - other allergies - a [fever](https://www.medicalnewstoday.com/articles/168266) - a bleeding disorder or take medications to thin the blood - a compromised immune system or take medication that affects the immune system - are pregnant, planning to become pregnant, or are breastfeeding - have already received another COVID-19 vaccine When considering the impact of the Pfizer vaccine, it is important to distinguish between its efficacy and its effectiveness. “Efficacy” refers to the vaccine’s performance under ideal and controlled circumstances, such as in clinical trials. “Effectiveness” refers to its performance in real-world situations. Efficacy There is strong evidence from clinical trials that the Pfizer vaccine has a high level of efficacy. A trial involving 43,548 participants, funded by BioNTech and Pfizer, reported that 2 doses of their vaccine confer [95% protection](https://www.nejm.org/doi/full/10.1056/NEJMoa2034577) against COVID-19 in people aged 16 years and older. Effectiveness This result was consistent across age groups, sexes, races, ethnicities, and body weights, as well as those with underlying medical conditions and people who have already had a SARS-CoV-2 infection. A [large study](https://www.nejm.org/doi/full/10.1056/NEJMoa2101765) on the Pfizer vaccine involving about 1.2 million people in Israel supports the findings of clinical trials. It indicates that two doses of the vaccine reduce symptomatic cases of COVID-19 by 94% across all age groups after 7 days of receiving the second dose. The vaccine also reduces severe illness by 92%. What about new variants? In some parts of the world, new variants of the SARS-CoV-2 virus have emerged. While concerning, this is normal because viruses evolve over time. It is likely that the Pfizer vaccine will still be effective against current variants. A [preview of a paper](https://www.biorxiv.org/content/10.1101/2021.01.07.425740v1) that looks at one particular mutation, present in variants first identified in the United Kingdom and South Africa, suggests that the Pfizer vaccine still works against them. Research to date indicates that the Pfizer vaccine is safe for those who are eligible for it. Its manufacturers developed the vaccine according to international safety standards. This vaccine has full authorization from the FDA and the European Medical Association. Some people may experience temporary side effects after receiving the Pfizer vaccine, which may last [a few days](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html). These include: - pain and swelling around the injection site - chills - fever - a [headache](https://www.medicalnewstoday.com/articles/73936) - [tiredness](https://www.medicalnewstoday.com/articles/248002) Usually, these side effects indicate that the vaccine is working and are signs that the immune system is responding to it. - muscle pain - joint pain - nausea - swollen lymph nodes - allergic reactions Side effects are [more common](https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/pfizer-biontech-covid-19-vaccine) after the second dose than the first dose. If a person experiences side effects after vaccination, they can take steps to care for themselves. Cool compresses and exercising the arm may ease pain and swelling while staying cool, and drinking fluids can help with a fever. People can also discuss trying over-the-counter (OTC) pain medications, such as acetaminophen, with a doctor or pharmacist. In rare cases, people can experience a severe allergic reaction up to [60 minutes](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7808711/) after receiving the vaccine. Signs and symptoms include: - breathing difficulties - dizziness - rapid heartbeat - rash all over the body - swelling of the face and throat - weakness Other [rare side effects](https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-june-25-2021) following vaccination can include myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the tissue surrounding the heart). These side effects are more likely following the second dose of the vaccine. If a person experiences any of the above symptoms, dial 911 or call a local emergency department immediately. Based on how mRNA vaccines work, the [CDC](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/pregnancy.html) do not believe they pose a specific risk during pregnancy. However, there is currently limited evidence to confirm this. [Animal studies](https://www.acog.org/covid-19/covid-19-vaccines-and-pregnancy-conversation-guide-for-clinicians) on the effects of the Pfizer vaccine found no direct or indirect risks to pregnancy or the health of the fetus. Another mRNA vaccine by Moderna had similar results. In February 2021, Pfizer and BioNTech announced they would begin human trials, testing their COVID-19 vaccine on [4,000](https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-commence-global-clinical-trial-evaluate) healthy pregnant adult females. These trials are still ongoing. If someone is unsure whether they should get the Pfizer vaccine due to being pregnant, they can discuss their concerns with a doctor. Some may be more comfortable waiting for the results of human trials, while others may want to get a vaccine as soon as they can. COVID-19 [does pose](https://www.acog.org/covid-19/covid-19-vaccines-and-pregnancy-conversation-guide-for-clinicians) an increased risk of severe illness during pregnancy. The Moderna and Pfizer vaccines have similar efficacy rates in clinical trials and involve receiving two shots several weeks apart. The table below outlines the differences: \| \| Pfizer \| Moderna \| \|---\|---\|---\| \| Age \| [12 and up](https://www.cdc.gov/vaccines/covid-19/info-by-product/pfizer/index.html) \| [18 and up](https://www.cdc.gov/vaccines/covid-19/info-by-product/moderna/index.html) \| \| Dosage \| two shots, 21 days apart \| two shots, 28 days apart \| \| Efficacy \| [95%](https://www.nejm.org/doi/full/10.1056/NEJMoa2034577) after two doses \| [92%](https://www.who.int/news-room/feature-stories/detail/the-moderna-covid-19-mrna-1273-vaccine-what-you-need-to-know) 14 days after the first dose \| \| Storage \| In an ultra-cold freezer at -112°F to -76°F (-80°C to -60°C), or at –[25°C to -15°C (-13°F to 5°F)](https://www.fda.gov/media/144413/download) for up to 2 weeks \| In a freezer between -13° F and 5°F, or in the refrigerator between 36°F and 46°F (2°C and 8°C) for up to 30 days \| Large-scale clinical trials are underway for two other COVID-19 vaccines from: - AstraZeneca - Novavax The AstraZeneca vaccination has an efficacy of [63\.09%](https://www.who.int/news-room/feature-stories/detail/the-oxford-astrazeneca-covid-19-vaccine-what-you-need-to-know) against symptomatic COVID-19. It requires two doses, given 8–12 weeks apart. A longer interval in between doses has associations with greater efficacy. Novavax reported that their COVID-19 vaccine candidate shows [89\.3%](https://ir.novavax.com/news-releases/news-release-details/novavax-covid-19-vaccine-demonstrates-893-efficacy-uk-phase-3) efficacy in U.K. phase three trials. Research indicates that the vaccine efficacy might be [86%](https://www.bmj.com/content/372/bmj.n296) against the variant first identified in the U.K., and 60% against the variant first identified in South Africa. The main benefit of getting a COVID-19 vaccine is protection from the disease, its symptoms, and its complications. COVID-19 has a wide range of effects on the body. For some, it is a mild short-term illness. For others, it is severe and can be life threatening. Some people also go on to experience [long COVID](https://www.medicalnewstoday.com/articles/long-term-effects-of-coronavirus), which can last for weeks or months. People who have received a vaccine may also be [less likely](https://www.who.int/news-room/q-a-detail/coronavirus-disease-\(covid-19\)-vaccines) to transmit the virus that causes the COVID-19 to other people, reducing the risk of others getting sick, particularly vulnerable people. Mass vaccination may also allow people to see their friends and family or go back to work sooner. However, no COVID-19 vaccine is 100% effective, so there is still some risk for those who receive a vaccine. Additionally, at present, scientists are unclear how long protection from vaccines lasts. Even if a person has received two doses, they [still need](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/faq.html) to follow safety guidelines for their local area, such as: - physical distancing - hand washing - wearing a mask Getting a vaccine is not compulsory. However, people who do not get a vaccine are at increased risk of developing COVID-19 than those who receive one. Some people are unable to get a COVID-19 vaccine for health reasons. Other people may choose not to. The [FDA](https://www.fda.gov/media/144638/download) state that it is an individual choice as to whether someone does or does not receive a COVID-19 vaccine. Choosing not to receive a vaccine will not impact their standard of medical care in the U.S. People who do not get a vaccine should take care to follow safety guidelines to reduce the risk. The Pfizer vaccine for the novel coronavirus, SARS-CoV-2, appears to be effective in clinical trials and real-world situations. Current evidence shows it is safe for most adults. Common side effects include chills, fever, tiredness, headache, and pain or swelling at the injection site. This should only last a few days. People can discuss different vaccines and their safety with a healthcare professional. People still need to wear masks, practice physical distancing, and follow hygiene guidelines to prevent transmission until advised otherwise. *For live updates on the latest developments regarding the novel [coronavirus](https://www.medicalnewstoday.com/articles/256521) and COVID-19, click [here](https://www.medicalnewstoday.com/articles/live-updates-coronavirus-covid-19)*.
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