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Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 179 (from laksa126)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa179.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://publichealth.jhu.edu/2020/side-effects-and-covid-19-vaccines-what-to-expect\')), getAhrefsUnparsedNoserviceFromURL(\'https://publichealth.jhu.edu/2020/side-effects-and-covid-19-vaccines-what-to-expect\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/publichealth.jhu.edu\/2020\/side-effects-and-covid-19-vaccines-what-to-expect","crawl_time":1776132158,"first_indexed_time":1629797441,"http_code":200,"src_unparsed":"edu,jhu!publichealth,\/2020\/side-effects-and-covid-19-vaccines-what-to-expect s443","src_root_hash":"6599457417117746179","history_drop_reason":null,"meta_title":"Side Effects and COVID-19 Vaccines: What to Expect | Johns Hopkins | Bloomberg School of Public Health","meta_descriptions":["It’s totally normal to experience side effects from COVID-19 vaccines. Here’s what you need to know."],"attrs_boilerpipe_text":"It’s totally normal to experience side effects from COVID-19 vaccines. Here’s what you need to know.\nA Q&A WITH \nWILLIAM MOSS\n(link is external)\nCOVID-19 vaccines are the first to be produced using the mRNA platform.\nThese vaccines are highly effective, but they are also “reactogenic,” meaning that they’re likely to cause a noticeable immune response.\nIn this Q&A, expert epidemiologist and executive director of the International Vaccine Access Center \nWilliam Moss, MD\n(link is external)\n, MPH, answers questions about side effects of COVID-19 vaccines, what to know before and after your vaccination, and when to contact your doctor or a medical professional.\nFor more information, please visit the CDC’s resource, “\nWhat to Expect After Getting a COVID-19 Vaccine\n(link is external)\n.”\nWhat side effects should I expect from COVID-19 vaccines?\nSide effects may vary with the type of COVID-19 vaccine. We know the most about side effects following vaccination with the Pfizer and Moderna messenger RNA—or mRNA—vaccines. \nThe most common side effect is soreness at the site of injection. Other side effects include fatigue, headache, muscle aches, chills, joint pain, and possibly some fever.\nHow long do side effects last?\nUsually 24 to 48 hours, and no more than a few days.\nSince COVID-19 vaccines come in two doses, will I experience the same side effects after each dose?\nSide effects were more frequent after the second dose in the vaccine trials.\nDo the side effects differ from one manufacturer’s vaccine to another?\nSide effects are similar after the Pfizer and Moderna mRNA vaccines but could differ with other types of vaccines.\nWhy do these vaccines seem to have more noticeable side effects than the flu vaccine? How do they compare to other vaccines’ side effects—like the shingles vaccine, for example?\nThese side effects are typical of the inflammation induced by vaccines and are a sign of the body’s immune response to the vaccine.\nSome vaccines are more reactogenic—the term used to describe these types of side effects—and some people have more severe reactions than others. The side effects of COVID-19 vaccines are similar to what is observed after the shingles vaccine.\nCan side effects be more pronounced in people who are at higher risk of severe COVID-19 disease—i.e., people who are older, have comorbidities, etc.?\nNo—in fact, vaccine side effects have been less frequent and severe in adults older than 55 years in the vaccine trials.\nDo children experience side effects from COVID-19 vaccines?\nChildren younger than 12 years of age have not yet received vaccines in clinical trials, so we do not yet know.\nHow do I know if what I am experiencing is normal or if I should alert my doctor or health care provider?\nYou will be told about the side effects of the vaccine and when you should consult a health care worker at the time you are vaccinated.\nThe \nCenters for Disease Control and Prevention\n(link is external)\n advises that you should contact your doctor or health care provider if the redness or tenderness where you got the shot increases after 24 hours, or if your side effects are worrying you or do not seem to be going away after a few days.\nIs it possible for me to contract COVID-19 between doses?\nYes—and this is why it is important to continue to wear a mask, practice social distancing, and wash your hands. \nThe first dose will not provide complete protection, and it will take about seven days after your second dose before you will achieve a full protective level of immunity that develops in about 95% of vaccine recipients. If you are exposed to SARS-CoV-2 before this time, it is possible that you could develop COVID-19. \nEven once you have received both doses of the COVID-19 vaccine, it will still be important to continue practicing public health mitigation strategies like masks and distancing until the pandemic is under control and we know more about how the vaccines prevent transmission. \nHow will I know whether what I am experiencing are side effects or possible COVID-19 infection?\nThe side effects of the vaccine typically start within 12 to 24 hours of vaccination, but it may be difficult to tell the two apart if you become infected between vaccine doses.\nIf you experience side effects that last beyond 48 hours, you should contact your doctor or medical provider for advice. \nWilliam J. Moss, MD\n(link is external)\n, is the executive director of the \nInternational Vaccine Access Center\n(link is external)\n, deputy director of the \nMalaria Research Institute\n(link is external)\n, and a professor in the departments of \nEpidemiology\n(link is external)\n, \nInternational Health\n(link is external)\n, and \nMolecular Microbiology and Immunology\n(link is external)\n at the Johns Hopkins Bloomberg School of Public Health.\nPhoto at top: Joe Raedle\nRELATED CONTENT\nClarifying COVID-19 Terminology\nAn Update on COVID-19 Treatments: Monoclonal Antibodies, Convalescent Plasma, and Other Promising Developments\nCan COVID-19 Vaccines Be Mandatory in the U.S. and Who Decides?\n(link is external)","attrs_markdown":"[Johns Hopkins UniversityEst. 1876 America’s First Research University](https:\/\/150.jhu.edu\/)\n\n[Skip to main content](https:\/\/publichealth.jhu.edu\/2020\/side-effects-and-covid-19-vaccines-what-to-expect#main-content)\n\n- [Expand](https:\/\/publichealth.jhu.edu\/2020\/side-effects-and-covid-19-vaccines-what-to-expect) [Departments](https:\/\/publichealth.jhu.edu\/departments)\n  - 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[Biostatistics](https:\/\/publichealth.jhu.edu\/departments\/biostatistics)\n  - [Environmental Health and Engineering](https:\/\/publichealth.jhu.edu\/departments\/environmental-health-and-engineering)\n  - [Epidemiology](https:\/\/publichealth.jhu.edu\/departments\/epidemiology)\n  - [Health Policy and Management](https:\/\/publichealth.jhu.edu\/departments\/health-policy-and-management)\n  - [Health, Behavior and Society](https:\/\/publichealth.jhu.edu\/departments\/health-behavior-and-society)\n  - [International Health](https:\/\/publichealth.jhu.edu\/departments\/international-health)\n  - [Mental Health](https:\/\/publichealth.jhu.edu\/departments\/mental-health)\n  - [Molecular Microbiology and Immunology](https:\/\/publichealth.jhu.edu\/departments\/molecular-microbiology-and-immunology)\n  - [Population, Family and Reproductive Health](https:\/\/publichealth.jhu.edu\/departments\/population-family-and-reproductive-health)\n- [Faculty](https:\/\/publichealth.jhu.edu\/faculty\/directory\/list)\n- [Topics](https:\/\/publichealth.jhu.edu\/topics)\n\n- [Departments »](https:\/\/publichealth.jhu.edu\/departments)\n  - [Biochemistry and Molecular Biology](https:\/\/publichealth.jhu.edu\/departments\/biochemistry-and-molecular-biology)\n  - [Biostatistics](https:\/\/publichealth.jhu.edu\/departments\/biostatistics)\n  - [Environmental Health and Engineering](https:\/\/publichealth.jhu.edu\/departments\/environmental-health-and-engineering)\n  - [Epidemiology](https:\/\/publichealth.jhu.edu\/departments\/epidemiology)\n  - [Health Policy and Management](https:\/\/publichealth.jhu.edu\/departments\/health-policy-and-management)\n  - [Health, Behavior and Society](https:\/\/publichealth.jhu.edu\/departments\/health-behavior-and-society)\n  - [International Health](https:\/\/publichealth.jhu.edu\/departments\/international-health)\n  - [Mental Health](https:\/\/publichealth.jhu.edu\/departments\/mental-health)\n  - [Molecular Microbiology and Immunology](https:\/\/publichealth.jhu.edu\/departments\/molecular-microbiology-and-immunology)\n  - [Population, Family and Reproductive Health](https:\/\/publichealth.jhu.edu\/departments\/population-family-and-reproductive-health)\n- [Faculty](https:\/\/publichealth.jhu.edu\/faculty\/directory\/list)\n- [Topics](https:\/\/publichealth.jhu.edu\/topics)\n\nSearch\n\nBloomberg School\n\n# Side Effects and COVID-19 Vaccines: What to Expect\n\nPublished\n\nDecember 17, 2020\n\n[COVID-19](https:\/\/publichealth.jhu.edu\/topics\/covid-19-and-public-health)\n\n[Drugs](https:\/\/publichealth.jhu.edu\/topics\/drugs-and-public-health)\n\n[Infectious Diseases](https:\/\/publichealth.jhu.edu\/topics\/infectious-diseases-and-public-health)\n\n![Elderly woman getting a vaccine, photo credit, Joe Raedle](https:\/\/publichealth.jhu.edu\/sites\/default\/files\/styles\/article_feature\/public\/2021-07\/vaccine-side-effects.jpeg?h=f2862316&itok=qgiEJG88)\n\n## It’s totally normal to experience side effects from COVID-19 vaccines. Here’s what you need to know.\nA Q\\&A WITH [WILLIAM MOSS](https:\/\/www.jhsph.edu\/faculty\/directory\/profile\/497\/william-john-moss \"(opens in a new window)\")\n\nCOVID-19 vaccines are the first to be produced using the mRNA platform.\n\nThese vaccines are highly effective, but they are also “reactogenic,” meaning that they’re likely to cause a noticeable immune response.\n\nIn this Q\\&A, expert epidemiologist and executive director of the International Vaccine Access Center [William Moss, MD](https:\/\/www.jhsph.edu\/faculty\/directory\/profile\/497\/william-john-moss \"(opens in a new window)\"), MPH, answers questions about side effects of COVID-19 vaccines, what to know before and after your vaccination, and when to contact your doctor or a medical professional.\n\n***For more information, please visit the CDC’s resource, “[What to Expect After Getting a COVID-19 Vaccine](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/expect\/after.html \"(opens in a new window)\").”***\n***\n**What side effects should I expect from COVID-19 vaccines?**\n\nSide effects may vary with the type of COVID-19 vaccine. We know the most about side effects following vaccination with the Pfizer and Moderna messenger RNA—or mRNA—vaccines.\n\nThe most common side effect is soreness at the site of injection. Other side effects include fatigue, headache, muscle aches, chills, joint pain, and possibly some fever.\n\n**How long do side effects last?**\n\nUsually 24 to 48 hours, and no more than a few days.\n\n**Since COVID-19 vaccines come in two doses, will I experience the same side effects after each dose?**\n\nSide effects were more frequent after the second dose in the vaccine trials.\n\n**Do the side effects differ from one manufacturer’s vaccine to another?**\n\nSide effects are similar after the Pfizer and Moderna mRNA vaccines but could differ with other types of vaccines.\n\n**Why do these vaccines seem to have more noticeable side effects than the flu vaccine? How do they compare to other vaccines’ side effects—like the shingles vaccine, for example?**\n\nThese side effects are typical of the inflammation induced by vaccines and are a sign of the body’s immune response to the vaccine.\n\nSome vaccines are more reactogenic—the term used to describe these types of side effects—and some people have more severe reactions than others. The side effects of COVID-19 vaccines are similar to what is observed after the shingles vaccine.\n\n**Can side effects be more pronounced in people who are at higher risk of severe COVID-19 disease—i.e., people who are older, have comorbidities, etc.?**\n\nNo—in fact, vaccine side effects have been less frequent and severe in adults older than 55 years in the vaccine trials.\n\n**Do children experience side effects from COVID-19 vaccines?**\n\nChildren younger than 12 years of age have not yet received vaccines in clinical trials, so we do not yet know.\n\n**How do I know if what I am experiencing is normal or if I should alert my doctor or health care provider?**\n\nYou will be told about the side effects of the vaccine and when you should consult a health care worker at the time you are vaccinated.\n\nThe [Centers for Disease Control and Prevention](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/expect\/after.html \"(opens in a new window)\") advises that you should contact your doctor or health care provider if the redness or tenderness where you got the shot increases after 24 hours, or if your side effects are worrying you or do not seem to be going away after a few days.\n\n**Is it possible for me to contract COVID-19 between doses?**\n\nYes—and this is why it is important to continue to wear a mask, practice social distancing, and wash your hands.\n\nThe first dose will not provide complete protection, and it will take about seven days after your second dose before you will achieve a full protective level of immunity that develops in about 95% of vaccine recipients. If you are exposed to SARS-CoV-2 before this time, it is possible that you could develop COVID-19.\n\nEven once you have received both doses of the COVID-19 vaccine, it will still be important to continue practicing public health mitigation strategies like masks and distancing until the pandemic is under control and we know more about how the vaccines prevent transmission.\n\n**How will I know whether what I am experiencing are side effects or possible COVID-19 infection?**\n\nThe side effects of the vaccine typically start within 12 to 24 hours of vaccination, but it may be difficult to tell the two apart if you become infected between vaccine doses.\n\nIf you experience side effects that last beyond 48 hours, you should contact your doctor or medical provider for advice.\n\n*[William J. Moss, MD](https:\/\/www.jhsph.edu\/faculty\/directory\/profile\/497\/william-john-moss \"(opens in a new window)\"), is the executive director of the [International Vaccine Access Center](https:\/\/www.jhsph.edu\/ivac\/ \"(opens in a new window)\"), deputy director of the [Malaria Research Institute](https:\/\/malaria.jhsph.edu\/ \"(opens in a new window)\"), and a professor in the departments of [Epidemiology](https:\/\/www.jhsph.edu\/departments\/epidemiology\/ \"(opens in a new window)\"), [International Health](https:\/\/www.jhsph.edu\/departments\/international-health\/ \"(opens in a new window)\"), and [Molecular Microbiology and Immunology](https:\/\/www.jhsph.edu\/departments\/w-harry-feinstone-department-of-molecular-microbiology-and-immunology\/ \"(opens in a new window)\") at the Johns Hopkins Bloomberg School of Public Health.*\n***\nPhoto at top: Joe Raedle\n\n### RELATED CONTENT\n- [Clarifying COVID-19 Terminology](https:\/\/publichealth.jhu.edu\/2020\/clarifying-covid-19-terminology \"Clarifying COVID-19 Terminology\")\n- [An Update on COVID-19 Treatments: Monoclonal Antibodies, Convalescent Plasma, and Other Promising Developments](https:\/\/publichealth.jhu.edu\/2020\/an-update-on-covid-19-treatments-monoclonal-antibodies-convalescent-plasma-and-other-promising-developments \"An Update on COVID-19 Treatments: Monoclonal Antibodies, Convalescent Plasma, and Other Promising Developments\")\n- [Can COVID-19 Vaccines Be Mandatory in the U.S. and Who Decides?](https:\/\/www.jhsph.edu\/covid-19\/articles\/can-covid-19-vaccines-be-mandatory-in-the-u-s-and-who-decides.html \"(opens in a new window)\")\n\n## More from the Bloomberg School\n- [See latest headlines](https:\/\/publichealth.jhu.edu\/headlines)\n\n## Related Content\n[![A patient fills out a form while her blood and saliva are screened for Hepatitis C and HIV in Spencer, West Virginia, on September 28, 2017.](https:\/\/publichealth.jhu.edu\/sites\/default\/files\/styles\/related_content\/public\/2026-04\/hep-c.jpg?h=4f4378cb&itok=zR0m9KTH)](https:\/\/publichealth.jhu.edu\/2026\/what-to-know-about-hepatitis-c)\n\n### [What to Know About Hepatitis C](https:\/\/publichealth.jhu.edu\/2026\/what-to-know-about-hepatitis-c)\nApril 10, 2026\n\n[![Image of a white van with the Check It logo](https:\/\/publichealth.jhu.edu\/sites\/default\/files\/styles\/related_content\/public\/2026-04\/Check-It-van.jpg?h=96a96008&itok=wrnq2VNV)](https:\/\/publichealth.jhu.edu\/2026\/check-it-drug-checking-program-will-support-baltimore-citys-overdose-response-efforts)\n\n### [Check It Drug Checking Program Will Support Baltimore City’s Overdose Response Efforts](https:\/\/publichealth.jhu.edu\/2026\/check-it-drug-checking-program-will-support-baltimore-citys-overdose-response-efforts)\nApril 09, 2026\n\n### [Why Review of the U.S.’s Measles Elimination Status Has Been Delayed](https:\/\/publichealth.jhu.edu\/2026\/why-review-of-the-uss-measles-elimination-status-has-been-delayed)\nApril 09, 2026\n\n[![man's feet on scale](https:\/\/publichealth.jhu.edu\/sites\/default\/files\/styles\/related_content\/public\/2026-02\/GettyImages-2220445333-3.2-release-scale-weight-loss-glp-1.jpg?h=f321a05b&itok=8b785v-1)](https:\/\/publichealth.jhu.edu\/2026\/glp-1-weight-loss-drugs-comparably-effective-for-patients-across-age-race-and-starting-weight)\n\n### [GLP-1 Weight-Loss Drugs Comparably Effective for Patients Across Age, Race, and Starting Weight](https:\/\/publichealth.jhu.edu\/2026\/glp-1-weight-loss-drugs-comparably-effective-for-patients-across-age-race-and-starting-weight)\nMarch 02, 2026\n\n[![Veterinarian seated in front of client with small dog on her lap lets dog sniff his hand while he speaks to the client.](https:\/\/publichealth.jhu.edu\/sites\/default\/files\/styles\/related_content\/public\/2026-02\/pet-vaccines-veterinarian.jpg?h=f321a05b&itok=pykOpVbz)](https:\/\/publichealth.jhu.edu\/2026\/vaccinating-your-dog-or-cat-can-also-protect-you)\n\n### [Why We Vaccinate Our Dogs and Cats](https:\/\/publichealth.jhu.edu\/2026\/vaccinating-your-dog-or-cat-can-also-protect-you)\nFebruary 27, 2026\n\n**Johns Hopkins Bloomberg School of Public Health**  \n [615 N. Wolfe Street, Baltimore, MD 21205](https:\/\/goo.gl\/maps\/p6Eowe2n6W2FuJ3k7 \"(opens in a new window)\")\n\n## Footer social\n- [LinkedIn](https:\/\/www.linkedin.com\/school\/johns-hopkins-bloomberg-school-of-public-health\/ \"(opens in a new window)\")\n- [Facebook](https:\/\/www.facebook.com\/JohnsHopkinsSPH \"(opens in a new window)\")\n- [Instagram](https:\/\/www.instagram.com\/johnshopkinssph\/ \"(opens in a new window)\")\n- [BlueSky](https:\/\/bsky.app\/profile\/johnshopkinssph.bsky.social \"(opens in a new window)\")\n- [X (Formerly Twitter)](https:\/\/twitter.com\/JohnsHopkinsSPH \"(opens in a new window)\")\n- [Youtube](https:\/\/www.youtube.com\/user\/JohnsHopkinsSPH \"(opens in a new window)\")\n\n## Footer menu primary\n- [Offices & Services](https:\/\/publichealth.jhu.edu\/offices-and-services)\n- [Alumni](https:\/\/publichealth.jhu.edu\/alumni)\n- [Giving](https:\/\/publichealth.jhu.edu\/giving)\n- [Calendars](https:\/\/publichealth.jhu.edu\/calendars-at-the-bloomberg-school)\n- [Careers](https:\/\/publichealth.jhu.edu\/careers \"Job Opportunities and Career Resources\")\n- [Contact Us](https:\/\/publichealth.jhu.edu\/contact-us)\n\n## Footer menu secondary\n- [Centers & Institutes Directory](https:\/\/publichealth.jhu.edu\/centers-and-institutes-directory)\n- [My.PublicHealth](https:\/\/my.publichealth.jhu.edu\/)\n- [My.JH](https:\/\/my.jh.edu\/myJH\/ \"(opens in a new window)\")\n- [CoursePlus](https:\/\/courseplus.jhu.edu\/)\n- [Student Information System](https:\/\/sis.jhu.edu\/)\n\n[Johns Hopkins University](https:\/\/www.jhu.edu\/)\n\n## Footer menu extra\n- [Web Policies](https:\/\/publichealth.jhu.edu\/web-policies)\n- [Accessibility](https:\/\/accessibility.jhu.edu\/)\n- [Website Help](https:\/\/webhelp.publichealth.jhu.edu\/support\/tickets\/new)\n\n## We use cookies on this site to enhance your user experience.\nBy clicking the Accept button, you agree to us doing so.\n\nLearn more\n\nAccept\n\nNo, thanks","attrs_readable_markdown":"## It’s totally normal to experience side effects from COVID-19 vaccines. Here’s what you need to know.\nA Q\\&A WITH [WILLIAM MOSS](https:\/\/www.jhsph.edu\/faculty\/directory\/profile\/497\/william-john-moss \"(opens in a new window)\")\n\nCOVID-19 vaccines are the first to be produced using the mRNA platform.\n\nThese vaccines are highly effective, but they are also “reactogenic,” meaning that they’re likely to cause a noticeable immune response.\n\nIn this Q\\&A, expert epidemiologist and executive director of the International Vaccine Access Center [William Moss, MD](https:\/\/www.jhsph.edu\/faculty\/directory\/profile\/497\/william-john-moss \"(opens in a new window)\"), MPH, answers questions about side effects of COVID-19 vaccines, what to know before and after your vaccination, and when to contact your doctor or a medical professional.\n\n***For more information, please visit the CDC’s resource, “[What to Expect After Getting a COVID-19 Vaccine](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/expect\/after.html \"(opens in a new window)\").”***\n***\n**What side effects should I expect from COVID-19 vaccines?**\n\nSide effects may vary with the type of COVID-19 vaccine. We know the most about side effects following vaccination with the Pfizer and Moderna messenger RNA—or mRNA—vaccines.\n\nThe most common side effect is soreness at the site of injection. Other side effects include fatigue, headache, muscle aches, chills, joint pain, and possibly some fever.\n\n**How long do side effects last?**\n\nUsually 24 to 48 hours, and no more than a few days.\n\n**Since COVID-19 vaccines come in two doses, will I experience the same side effects after each dose?**\n\nSide effects were more frequent after the second dose in the vaccine trials.\n\n**Do the side effects differ from one manufacturer’s vaccine to another?**\n\nSide effects are similar after the Pfizer and Moderna mRNA vaccines but could differ with other types of vaccines.\n\n**Why do these vaccines seem to have more noticeable side effects than the flu vaccine? How do they compare to other vaccines’ side effects—like the shingles vaccine, for example?**\n\nThese side effects are typical of the inflammation induced by vaccines and are a sign of the body’s immune response to the vaccine.\n\nSome vaccines are more reactogenic—the term used to describe these types of side effects—and some people have more severe reactions than others. The side effects of COVID-19 vaccines are similar to what is observed after the shingles vaccine.\n\n**Can side effects be more pronounced in people who are at higher risk of severe COVID-19 disease—i.e., people who are older, have comorbidities, etc.?**\n\nNo—in fact, vaccine side effects have been less frequent and severe in adults older than 55 years in the vaccine trials.\n\n**Do children experience side effects from COVID-19 vaccines?**\n\nChildren younger than 12 years of age have not yet received vaccines in clinical trials, so we do not yet know.\n\n**How do I know if what I am experiencing is normal or if I should alert my doctor or health care provider?**\n\nYou will be told about the side effects of the vaccine and when you should consult a health care worker at the time you are vaccinated.\n\nThe [Centers for Disease Control and Prevention](https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/expect\/after.html \"(opens in a new window)\") advises that you should contact your doctor or health care provider if the redness or tenderness where you got the shot increases after 24 hours, or if your side effects are worrying you or do not seem to be going away after a few days.\n\n**Is it possible for me to contract COVID-19 between doses?**\n\nYes—and this is why it is important to continue to wear a mask, practice social distancing, and wash your hands.\n\nThe first dose will not provide complete protection, and it will take about seven days after your second dose before you will achieve a full protective level of immunity that develops in about 95% of vaccine recipients. If you are exposed to SARS-CoV-2 before this time, it is possible that you could develop COVID-19.\n\nEven once you have received both doses of the COVID-19 vaccine, it will still be important to continue practicing public health mitigation strategies like masks and distancing until the pandemic is under control and we know more about how the vaccines prevent transmission.\n\n**How will I know whether what I am experiencing are side effects or possible COVID-19 infection?**\n\nThe side effects of the vaccine typically start within 12 to 24 hours of vaccination, but it may be difficult to tell the two apart if you become infected between vaccine doses.\n\nIf you experience side effects that last beyond 48 hours, you should contact your doctor or medical provider for advice.\n\n*[William J. Moss, MD](https:\/\/www.jhsph.edu\/faculty\/directory\/profile\/497\/william-john-moss \"(opens in a new window)\"), is the executive director of the [International Vaccine Access Center](https:\/\/www.jhsph.edu\/ivac\/ \"(opens in a new window)\"), deputy director of the [Malaria Research Institute](https:\/\/malaria.jhsph.edu\/ \"(opens in a new window)\"), and a professor in the departments of [Epidemiology](https:\/\/www.jhsph.edu\/departments\/epidemiology\/ \"(opens in a new window)\"), [International Health](https:\/\/www.jhsph.edu\/departments\/international-health\/ \"(opens in a new window)\"), and [Molecular Microbiology and Immunology](https:\/\/www.jhsph.edu\/departments\/w-harry-feinstone-department-of-molecular-microbiology-and-immunology\/ \"(opens in a new window)\") at the Johns Hopkins Bloomberg School of Public Health.*\n***\nPhoto at top: Joe Raedle\n\n### RELATED CONTENT\n- [Clarifying COVID-19 Terminology](https:\/\/publichealth.jhu.edu\/2020\/clarifying-covid-19-terminology \"Clarifying COVID-19 Terminology\")\n- [An Update on COVID-19 Treatments: Monoclonal Antibodies, Convalescent Plasma, and Other Promising Developments](https:\/\/publichealth.jhu.edu\/2020\/an-update-on-covid-19-treatments-monoclonal-antibodies-convalescent-plasma-and-other-promising-developments \"An Update on COVID-19 Treatments: Monoclonal Antibodies, Convalescent Plasma, and Other Promising Developments\")\n- [Can COVID-19 Vaccines Be Mandatory in the U.S. and Who Decides?](https:\/\/www.jhsph.edu\/covid-19\/articles\/can-covid-19-vaccines-be-mandatory-in-the-u-s-and-who-decides.html \"(opens in a new window)\")","meta_canonical":null}

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Meta Title	Side Effects and COVID-19 Vaccines: What to Expect \| Johns Hopkins \| Bloomberg School of Public Health
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Boilerpipe Text	It’s totally normal to experience side effects from COVID-19 vaccines. Here’s what you need to know. A Q&A WITH WILLIAM MOSS (link is external) COVID-19 vaccines are the first to be produced using the mRNA platform. These vaccines are highly effective, but they are also “reactogenic,” meaning that they’re likely to cause a noticeable immune response. In this Q&A, expert epidemiologist and executive director of the International Vaccine Access Center William Moss, MD (link is external) , MPH, answers questions about side effects of COVID-19 vaccines, what to know before and after your vaccination, and when to contact your doctor or a medical professional. For more information, please visit the CDC’s resource, “ What to Expect After Getting a COVID-19 Vaccine (link is external) .” What side effects should I expect from COVID-19 vaccines? Side effects may vary with the type of COVID-19 vaccine. We know the most about side effects following vaccination with the Pfizer and Moderna messenger RNA—or mRNA—vaccines. The most common side effect is soreness at the site of injection. Other side effects include fatigue, headache, muscle aches, chills, joint pain, and possibly some fever. How long do side effects last? Usually 24 to 48 hours, and no more than a few days. Since COVID-19 vaccines come in two doses, will I experience the same side effects after each dose? Side effects were more frequent after the second dose in the vaccine trials. Do the side effects differ from one manufacturer’s vaccine to another? Side effects are similar after the Pfizer and Moderna mRNA vaccines but could differ with other types of vaccines. Why do these vaccines seem to have more noticeable side effects than the flu vaccine? How do they compare to other vaccines’ side effects—like the shingles vaccine, for example? These side effects are typical of the inflammation induced by vaccines and are a sign of the body’s immune response to the vaccine. Some vaccines are more reactogenic—the term used to describe these types of side effects—and some people have more severe reactions than others. The side effects of COVID-19 vaccines are similar to what is observed after the shingles vaccine. Can side effects be more pronounced in people who are at higher risk of severe COVID-19 disease—i.e., people who are older, have comorbidities, etc.? No—in fact, vaccine side effects have been less frequent and severe in adults older than 55 years in the vaccine trials. Do children experience side effects from COVID-19 vaccines? Children younger than 12 years of age have not yet received vaccines in clinical trials, so we do not yet know. How do I know if what I am experiencing is normal or if I should alert my doctor or health care provider? You will be told about the side effects of the vaccine and when you should consult a health care worker at the time you are vaccinated. The Centers for Disease Control and Prevention (link is external) advises that you should contact your doctor or health care provider if the redness or tenderness where you got the shot increases after 24 hours, or if your side effects are worrying you or do not seem to be going away after a few days. Is it possible for me to contract COVID-19 between doses? Yes—and this is why it is important to continue to wear a mask, practice social distancing, and wash your hands. The first dose will not provide complete protection, and it will take about seven days after your second dose before you will achieve a full protective level of immunity that develops in about 95% of vaccine recipients. If you are exposed to SARS-CoV-2 before this time, it is possible that you could develop COVID-19. Even once you have received both doses of the COVID-19 vaccine, it will still be important to continue practicing public health mitigation strategies like masks and distancing until the pandemic is under control and we know more about how the vaccines prevent transmission. How will I know whether what I am experiencing are side effects or possible COVID-19 infection? The side effects of the vaccine typically start within 12 to 24 hours of vaccination, but it may be difficult to tell the two apart if you become infected between vaccine doses. If you experience side effects that last beyond 48 hours, you should contact your doctor or medical provider for advice. William J. Moss, MD (link is external) , is the executive director of the International Vaccine Access Center (link is external) , deputy director of the Malaria Research Institute (link is external) , and a professor in the departments of Epidemiology (link is external) , International Health (link is external) , and Molecular Microbiology and Immunology (link is external) at the Johns Hopkins Bloomberg School of Public Health. Photo at top: Joe Raedle RELATED CONTENT Clarifying COVID-19 Terminology An Update on COVID-19 Treatments: Monoclonal Antibodies, Convalescent Plasma, and Other Promising Developments Can COVID-19 Vaccines Be Mandatory in the U.S. and Who Decides? (link is external)
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[International Health](https://publichealth.jhu.edu/departments/international-health) - [Mental Health](https://publichealth.jhu.edu/departments/mental-health) - [Molecular Microbiology and Immunology](https://publichealth.jhu.edu/departments/molecular-microbiology-and-immunology) - [Population, Family and Reproductive Health](https://publichealth.jhu.edu/departments/population-family-and-reproductive-health) - [Faculty](https://publichealth.jhu.edu/faculty/directory/list) - [Topics](https://publichealth.jhu.edu/topics) Search Bloomberg School # Side Effects and COVID-19 Vaccines: What to Expect Published December 17, 2020 [COVID-19](https://publichealth.jhu.edu/topics/covid-19-and-public-health) [Drugs](https://publichealth.jhu.edu/topics/drugs-and-public-health) [Infectious Diseases](https://publichealth.jhu.edu/topics/infectious-diseases-and-public-health) ![Elderly woman getting a vaccine, photo credit, Joe Raedle](https://publichealth.jhu.edu/sites/default/files/styles/article_feature/public/2021-07/vaccine-side-effects.jpeg?h=f2862316&itok=qgiEJG88) ## It’s totally normal to experience side effects from COVID-19 vaccines. Here’s what you need to know. A Q\&A WITH [WILLIAM MOSS](https://www.jhsph.edu/faculty/directory/profile/497/william-john-moss "(opens in a new window)") COVID-19 vaccines are the first to be produced using the mRNA platform. These vaccines are highly effective, but they are also “reactogenic,” meaning that they’re likely to cause a noticeable immune response. In this Q\&A, expert epidemiologist and executive director of the International Vaccine Access Center [William Moss, MD](https://www.jhsph.edu/faculty/directory/profile/497/william-john-moss "(opens in a new window)"), MPH, answers questions about side effects of COVID-19 vaccines, what to know before and after your vaccination, and when to contact your doctor or a medical professional. *For more information, please visit the CDC’s resource, “[What to Expect After Getting a COVID-19 Vaccine](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html "(opens in a new window)").”* * What side effects should I expect from COVID-19 vaccines? Side effects may vary with the type of COVID-19 vaccine. We know the most about side effects following vaccination with the Pfizer and Moderna messenger RNA—or mRNA—vaccines. The most common side effect is soreness at the site of injection. Other side effects include fatigue, headache, muscle aches, chills, joint pain, and possibly some fever. How long do side effects last? Usually 24 to 48 hours, and no more than a few days. Since COVID-19 vaccines come in two doses, will I experience the same side effects after each dose? Side effects were more frequent after the second dose in the vaccine trials. Do the side effects differ from one manufacturer’s vaccine to another? Side effects are similar after the Pfizer and Moderna mRNA vaccines but could differ with other types of vaccines. Why do these vaccines seem to have more noticeable side effects than the flu vaccine? How do they compare to other vaccines’ side effects—like the shingles vaccine, for example? These side effects are typical of the inflammation induced by vaccines and are a sign of the body’s immune response to the vaccine. Some vaccines are more reactogenic—the term used to describe these types of side effects—and some people have more severe reactions than others. The side effects of COVID-19 vaccines are similar to what is observed after the shingles vaccine. Can side effects be more pronounced in people who are at higher risk of severe COVID-19 disease—i.e., people who are older, have comorbidities, etc.? No—in fact, vaccine side effects have been less frequent and severe in adults older than 55 years in the vaccine trials. Do children experience side effects from COVID-19 vaccines? Children younger than 12 years of age have not yet received vaccines in clinical trials, so we do not yet know. How do I know if what I am experiencing is normal or if I should alert my doctor or health care provider? You will be told about the side effects of the vaccine and when you should consult a health care worker at the time you are vaccinated. The [Centers for Disease Control and Prevention](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html "(opens in a new window)") advises that you should contact your doctor or health care provider if the redness or tenderness where you got the shot increases after 24 hours, or if your side effects are worrying you or do not seem to be going away after a few days. Is it possible for me to contract COVID-19 between doses? Yes—and this is why it is important to continue to wear a mask, practice social distancing, and wash your hands. The first dose will not provide complete protection, and it will take about seven days after your second dose before you will achieve a full protective level of immunity that develops in about 95% of vaccine recipients. If you are exposed to SARS-CoV-2 before this time, it is possible that you could develop COVID-19. Even once you have received both doses of the COVID-19 vaccine, it will still be important to continue practicing public health mitigation strategies like masks and distancing until the pandemic is under control and we know more about how the vaccines prevent transmission. How will I know whether what I am experiencing are side effects or possible COVID-19 infection?** The side effects of the vaccine typically start within 12 to 24 hours of vaccination, but it may be difficult to tell the two apart if you become infected between vaccine doses. If you experience side effects that last beyond 48 hours, you should contact your doctor or medical provider for advice. [William J. Moss, MD](https://www.jhsph.edu/faculty/directory/profile/497/william-john-moss "(opens in a new window)"), is the executive director of the [International Vaccine Access Center](https://www.jhsph.edu/ivac/ "(opens in a new window)"), deputy director of the [Malaria Research Institute](https://malaria.jhsph.edu/ "(opens in a new window)"), and a professor in the departments of [Epidemiology](https://www.jhsph.edu/departments/epidemiology/ "(opens in a new window)"), [International Health](https://www.jhsph.edu/departments/international-health/ "(opens in a new window)"), and [Molecular Microbiology and Immunology](https://www.jhsph.edu/departments/w-harry-feinstone-department-of-molecular-microbiology-and-immunology/ "(opens in a new window)") at the Johns Hopkins Bloomberg School of Public Health. * Photo at top: Joe Raedle ### RELATED CONTENT - [Clarifying COVID-19 Terminology](https://publichealth.jhu.edu/2020/clarifying-covid-19-terminology "Clarifying COVID-19 Terminology") - [An Update on COVID-19 Treatments: Monoclonal Antibodies, Convalescent Plasma, and Other Promising Developments](https://publichealth.jhu.edu/2020/an-update-on-covid-19-treatments-monoclonal-antibodies-convalescent-plasma-and-other-promising-developments "An Update on COVID-19 Treatments: Monoclonal Antibodies, Convalescent Plasma, and Other Promising Developments") - [Can COVID-19 Vaccines Be Mandatory in the U.S. and Who Decides?](https://www.jhsph.edu/covid-19/articles/can-covid-19-vaccines-be-mandatory-in-the-u-s-and-who-decides.html "(opens in a new window)") ## More from the Bloomberg School - [See latest headlines](https://publichealth.jhu.edu/headlines) ## Related Content [![A patient fills out a form while her blood and saliva are screened for Hepatitis C and HIV in Spencer, West Virginia, on September 28, 2017.](https://publichealth.jhu.edu/sites/default/files/styles/related_content/public/2026-04/hep-c.jpg?h=4f4378cb&itok=zR0m9KTH)](https://publichealth.jhu.edu/2026/what-to-know-about-hepatitis-c) ### [What to Know About Hepatitis C](https://publichealth.jhu.edu/2026/what-to-know-about-hepatitis-c) April 10, 2026 [![Image of a white van with the Check It logo](https://publichealth.jhu.edu/sites/default/files/styles/related_content/public/2026-04/Check-It-van.jpg?h=96a96008&itok=wrnq2VNV)](https://publichealth.jhu.edu/2026/check-it-drug-checking-program-will-support-baltimore-citys-overdose-response-efforts) ### [Check It Drug Checking Program Will Support Baltimore City’s Overdose Response Efforts](https://publichealth.jhu.edu/2026/check-it-drug-checking-program-will-support-baltimore-citys-overdose-response-efforts) April 09, 2026 ### [Why Review of the U.S.’s Measles Elimination Status Has Been Delayed](https://publichealth.jhu.edu/2026/why-review-of-the-uss-measles-elimination-status-has-been-delayed) April 09, 2026 [![man's feet on scale](https://publichealth.jhu.edu/sites/default/files/styles/related_content/public/2026-02/GettyImages-2220445333-3.2-release-scale-weight-loss-glp-1.jpg?h=f321a05b&itok=8b785v-1)](https://publichealth.jhu.edu/2026/glp-1-weight-loss-drugs-comparably-effective-for-patients-across-age-race-and-starting-weight) ### [GLP-1 Weight-Loss Drugs Comparably Effective for Patients Across Age, Race, and Starting Weight](https://publichealth.jhu.edu/2026/glp-1-weight-loss-drugs-comparably-effective-for-patients-across-age-race-and-starting-weight) March 02, 2026 [![Veterinarian seated in front of client with small dog on her lap lets dog sniff his hand while he speaks to the client.](https://publichealth.jhu.edu/sites/default/files/styles/related_content/public/2026-02/pet-vaccines-veterinarian.jpg?h=f321a05b&itok=pykOpVbz)](https://publichealth.jhu.edu/2026/vaccinating-your-dog-or-cat-can-also-protect-you) ### [Why We Vaccinate Our Dogs and Cats](https://publichealth.jhu.edu/2026/vaccinating-your-dog-or-cat-can-also-protect-you) February 27, 2026 Johns Hopkins Bloomberg School of Public Health** [615 N. 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Readable Markdown	## It’s totally normal to experience side effects from COVID-19 vaccines. Here’s what you need to know. A Q\&A WITH [WILLIAM MOSS](https://www.jhsph.edu/faculty/directory/profile/497/william-john-moss "(opens in a new window)") COVID-19 vaccines are the first to be produced using the mRNA platform. These vaccines are highly effective, but they are also “reactogenic,” meaning that they’re likely to cause a noticeable immune response. In this Q\&A, expert epidemiologist and executive director of the International Vaccine Access Center [William Moss, MD](https://www.jhsph.edu/faculty/directory/profile/497/william-john-moss "(opens in a new window)"), MPH, answers questions about side effects of COVID-19 vaccines, what to know before and after your vaccination, and when to contact your doctor or a medical professional. *For more information, please visit the CDC’s resource, “[What to Expect After Getting a COVID-19 Vaccine](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html "(opens in a new window)").”* * What side effects should I expect from COVID-19 vaccines? Side effects may vary with the type of COVID-19 vaccine. We know the most about side effects following vaccination with the Pfizer and Moderna messenger RNA—or mRNA—vaccines. The most common side effect is soreness at the site of injection. Other side effects include fatigue, headache, muscle aches, chills, joint pain, and possibly some fever. How long do side effects last? Usually 24 to 48 hours, and no more than a few days. Since COVID-19 vaccines come in two doses, will I experience the same side effects after each dose? Side effects were more frequent after the second dose in the vaccine trials. Do the side effects differ from one manufacturer’s vaccine to another? Side effects are similar after the Pfizer and Moderna mRNA vaccines but could differ with other types of vaccines. Why do these vaccines seem to have more noticeable side effects than the flu vaccine? How do they compare to other vaccines’ side effects—like the shingles vaccine, for example? These side effects are typical of the inflammation induced by vaccines and are a sign of the body’s immune response to the vaccine. Some vaccines are more reactogenic—the term used to describe these types of side effects—and some people have more severe reactions than others. The side effects of COVID-19 vaccines are similar to what is observed after the shingles vaccine. Can side effects be more pronounced in people who are at higher risk of severe COVID-19 disease—i.e., people who are older, have comorbidities, etc.? No—in fact, vaccine side effects have been less frequent and severe in adults older than 55 years in the vaccine trials. Do children experience side effects from COVID-19 vaccines? Children younger than 12 years of age have not yet received vaccines in clinical trials, so we do not yet know. How do I know if what I am experiencing is normal or if I should alert my doctor or health care provider? You will be told about the side effects of the vaccine and when you should consult a health care worker at the time you are vaccinated. The [Centers for Disease Control and Prevention](https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html "(opens in a new window)") advises that you should contact your doctor or health care provider if the redness or tenderness where you got the shot increases after 24 hours, or if your side effects are worrying you or do not seem to be going away after a few days. Is it possible for me to contract COVID-19 between doses? Yes—and this is why it is important to continue to wear a mask, practice social distancing, and wash your hands. The first dose will not provide complete protection, and it will take about seven days after your second dose before you will achieve a full protective level of immunity that develops in about 95% of vaccine recipients. If you are exposed to SARS-CoV-2 before this time, it is possible that you could develop COVID-19. Even once you have received both doses of the COVID-19 vaccine, it will still be important to continue practicing public health mitigation strategies like masks and distancing until the pandemic is under control and we know more about how the vaccines prevent transmission. How will I know whether what I am experiencing are side effects or possible COVID-19 infection?** The side effects of the vaccine typically start within 12 to 24 hours of vaccination, but it may be difficult to tell the two apart if you become infected between vaccine doses. If you experience side effects that last beyond 48 hours, you should contact your doctor or medical provider for advice. [William J. Moss, MD](https://www.jhsph.edu/faculty/directory/profile/497/william-john-moss "(opens in a new window)"), is the executive director of the [International Vaccine Access Center](https://www.jhsph.edu/ivac/ "(opens in a new window)"), deputy director of the [Malaria Research Institute](https://malaria.jhsph.edu/ "(opens in a new window)"), and a professor in the departments of [Epidemiology](https://www.jhsph.edu/departments/epidemiology/ "(opens in a new window)"), [International Health](https://www.jhsph.edu/departments/international-health/ "(opens in a new window)"), and [Molecular Microbiology and Immunology](https://www.jhsph.edu/departments/w-harry-feinstone-department-of-molecular-microbiology-and-immunology/ "(opens in a new window)") at the Johns Hopkins Bloomberg School of Public Health. *** Photo at top: Joe Raedle ### RELATED CONTENT - [Clarifying COVID-19 Terminology](https://publichealth.jhu.edu/2020/clarifying-covid-19-terminology "Clarifying COVID-19 Terminology") - [An Update on COVID-19 Treatments: Monoclonal Antibodies, Convalescent Plasma, and Other Promising Developments](https://publichealth.jhu.edu/2020/an-update-on-covid-19-treatments-monoclonal-antibodies-convalescent-plasma-and-other-promising-developments "An Update on COVID-19 Treatments: Monoclonal Antibodies, Convalescent Plasma, and Other Promising Developments") - [Can COVID-19 Vaccines Be Mandatory in the U.S. and Who Decides?](https://www.jhsph.edu/covid-19/articles/can-covid-19-vaccines-be-mandatory-in-the-u-s-and-who-decides.html "(opens in a new window)")
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