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 [Harvard Health Publishing ](https://www.health.harvard.edu/) [Harvard Health Publishing](https://www.health.harvard.edu/) [HarvardHealthOnline+](https://www.health.harvard.edu/hho-plus?utm_source=site&utm_medium=web&utm_campaign=top_button) Search [Customer Service](https://www.health.harvard.edu/customer-service) [Content Licensing](https://www.health.harvard.edu/licensing) [About Us](https://www.health.harvard.edu/about-us) [Log In](https://www.health.harvard.edu/login) Open mobile menu [Free HealthBeat Signup](https://www.health.harvard.edu/healthbeat) Shop [Subscriptions](https://www.health.harvard.edu/subscribe) [Special Health Reports](https://www.health.harvard.edu/special-health-reports) [Online Courses](https://www.harvardhealthonlinelearning.com/catalog) [Pay Subscription Bill](https://www.health.harvard.edu/pay-bill) [Common Conditions](https://www.health.harvard.edu/category/common-conditions) [Staying Healthy](https://www.health.harvard.edu/category/staying-healthy) [Resources](https://www.health.harvard.edu/resources) [Blog](https://www.health.harvard.edu/blog) [COVID-19 Updates](https://www.health.harvard.edu/diseases-and-conditions/coronavirus-resource-center) Close menu [HarvardHealthOnline+](https://www.health.harvard.edu/hho-plus?utm_source=site&utm_medium=web&utm_campaign=mobile_button) ## Main Content - [Common Conditions](https://www.health.harvard.edu/category/common-conditions) - [Staying Healthy](https://www.health.harvard.edu/category/staying-healthy) - [Resources](https://www.health.harvard.edu/resources) - [Blog](https://www.health.harvard.edu/blog) ## Helpful Links - [Customer Service](https://www.health.harvard.edu/customer-service) - [About Us](https://www.health.harvard.edu/about-us) - [Content Licensing](https://www.health.harvard.edu/licensing) - [Free Healthbeat Signup](https://www.health.harvard.edu/healthbeat) - [Subscriptions](https://www.health.harvard.edu/subscribe) - [Special Health Reports](https://www.health.harvard.edu/special-health-reports) - [Online Courses](https://www.harvardhealthonlinelearning.com/) - [Pay Subscription Bill](https://www.health.harvard.edu/pay-bill) Close Recent Articles [ Trying to lose weight? Be careful not to lose muscle](https://www.health.harvard.edu/staying-healthy/trying-to-lose-weight-be-careful-not-to-lose-muscle) [ Is your skin problem actually an autoimmune condition?](https://www.health.harvard.edu/diseases-and-conditions/is-your-skin-problem-actually-an-autoimmune-condition) [ People with diabetes face higher risk of hearing loss](https://www.health.harvard.edu/diseases-and-conditions/people-with-diabetes-face-higher-risk-of-hearing-loss) [ Antibiotic-free fixes for recurrent UTIs](https://www.health.harvard.edu/womens-health/antibiotic-free-fixes-for-recurrent-utis) [ Musculoskeletal syndrome of menopause: When menopause makes you ache all over](https://www.health.harvard.edu/womens-health/musculoskeletal-syndrome-of-menopause-when-menopause-makes-you-ache-all-over) [ When can older women stop getting mammograms?](https://www.health.harvard.edu/womens-health/when-can-older-women-stop-getting-mammograms) [ To lose weight, especially harmful belly fat, combine diet and exercise](https://www.health.harvard.edu/staying-healthy/to-lose-weight-especially-harmful-belly-fat-combine-diet-and-exercise) [ Can men hold off on treating recurring prostate cancer?](https://www.health.harvard.edu/blog/can-men-hold-off-on-treating-recurring-prostate-cancer-202512193108) [ The 7 types of rest and why we need them all](https://www.health.harvard.edu/mind-and-mood/the-7-types-of-rest-and-why-we-need-them-all) [ What are the early warning signs of cervical cancer?](https://www.health.harvard.edu/cancer/what-are-the-early-warning-signs-of-cervical-cancer) 1 / 10 [Staying Healthy](https://www.health.harvard.edu/topics/staying-healthy) # Side effects after a COVID shot indicate it's working ## In the journals September 1, 2024 By [Matthew Solan](https://www.health.harvard.edu/authors/matthew-solan), Former Executive Editor, [*Harvard Men's Health Watch*](https://www.health.harvard.edu/mens) - Reviewed by [Howard E. LeWine, MD](https://www.health.harvard.edu/authors/howard-lewine-md), Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing Share [Share this page to Facebook](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.health.harvard.edu%2Fstaying-healthy%2Fside-effects-after-a-covid-shot-indicate-its-working&display=popup) [Share this page to X](https://twitter.com/intent/tweet?original_referer=https%3A%2F%2Fwww.health.harvard.edu%2Fstaying-healthy%2Fside-effects-after-a-covid-shot-indicate-its-working&text=Side%20effects%20after%20a%20COVID%20shot%20indicate%20it's%20working%20-%20Harvard%20Health&tw_p=tweetbutton&url=https%3A%2F%2Fwww.health.harvard.edu%2Fstaying-healthy%2Fside-effects-after-a-covid-shot-indicate-its-working) [Share this page via Email](<mailto:?subject=Great health news for you from the experts at Harvard&body=Check out this link from Harvard Health: Side effects after a COVID shot indicate it's working - https://www.health.harvard.edu/staying-healthy/side-effects-after-a-covid-shot-indicate-its-working>) Copy this page to clipboard Print This Page Click to Print  One reason people avoid getting a COVID booster is concern about side effects like fatigue, achiness, muscle and joint pain, chills, headache, and fever. But a new study found that these symptoms indicate a robust immune response to the vaccine that increases antibody levels and offers extra protection against the virus. Researchers examined the antibody responses and side effects from 363 people who had the two-dose Pfizer-BioNTech or Moderna mRNA vaccines. One month after the second dose, they found that those who cited at least one side effect, such as chills, fatigue, headache, or generally feeling unwell, had antibody levels 1.4 to 1.6 times higher than those who reported no symptoms. The researchers found that these levels were still elevated six months later. Of note, COVID vaccines increase antibody levels in almost everyone who gets vaccinated even if they have no symptoms. The study was published online June 10, 2024, by *Annals of Internal Medicine*. Smart strategies for achieving and maintaining a healthy weight  ## Lose Weight and Keep It Off Successful weight loss depends largely on becoming more aware of your behaviors and starting to change them. Instead of relying on willpower, this process demands skill power. This Special Health Report, Lose Weight and Keep It Off, offers a range of solutions that have worked for many people and can be tailored to your needs. [Learn More\!](https://servedbyadbutler.com/redirect.spark?MID=186626&plid=2650436&setID=812675&channelID=0&CID=862911&banID=524318303&PID=0&textadID=0&tc=1&rnd=5115410464&scheduleID=3647184&adSize=0x0&matches=%5B%22healthy%22%5D&mt=1770424691068704&spr=1&referrer=https%3A%2F%2Fwww.health.harvard.edu%2Fstaying-healthy%2Fside-effects-after-a-covid-shot-indicate-its-working&request_uuid=b94f71c5-774f-448e-9e28-95a7dfc9e7ca&hc=7d4828dbb37523b8538837a11b71c31d762f209f&location=) **Image: © Jacob Wackerhausen/Getty Images** ## About the Author  Matthew Solan, Former Executive Editor, [*Harvard Men's Health Watch*](https://www.health.harvard.edu/mens) Matthew Solan is the former executive editor of Harvard Men’s Health Watch. He previously served as executive editor for UCLA Health’s Healthy Years and as a contributor to Duke Medicine’s Health News and Weill Cornell Medical … [See Full Bio](https://www.health.harvard.edu/authors/matthew-solan) [View all posts by Matthew Solan](https://www.health.harvard.edu/authors/matthew-solan) ## About the Reviewer  Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. [See Full Bio](https://www.health.harvard.edu/authors/howard-lewine-md) [View all posts by Howard E. LeWine, MD](https://www.health.harvard.edu/authors/howard-lewine-md) Share [Share this page to Facebook](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.health.harvard.edu%2Fstaying-healthy%2Fside-effects-after-a-covid-shot-indicate-its-working&display=popup) [Share this page to X](https://twitter.com/intent/tweet?original_referer=https%3A%2F%2Fwww.health.harvard.edu%2Fstaying-healthy%2Fside-effects-after-a-covid-shot-indicate-its-working&text=Side%20effects%20after%20a%20COVID%20shot%20indicate%20it's%20working%20-%20Harvard%20Health&tw_p=tweetbutton&url=https%3A%2F%2Fwww.health.harvard.edu%2Fstaying-healthy%2Fside-effects-after-a-covid-shot-indicate-its-working) [Share this page via Email](<mailto:?subject=Great health news for you from the experts at Harvard&body=Check out this link from Harvard Health: Side effects after a COVID shot indicate it's working - https://www.health.harvard.edu/staying-healthy/side-effects-after-a-covid-shot-indicate-its-working>) Copy this page to clipboard Print This Page Click to Print ## Disclaimer: As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician. Recent Articles [ Trying to lose weight? Be careful not to lose muscle](https://www.health.harvard.edu/staying-healthy/trying-to-lose-weight-be-careful-not-to-lose-muscle) [ Is your skin problem actually an autoimmune condition?](https://www.health.harvard.edu/diseases-and-conditions/is-your-skin-problem-actually-an-autoimmune-condition) [ People with diabetes face higher risk of hearing loss](https://www.health.harvard.edu/diseases-and-conditions/people-with-diabetes-face-higher-risk-of-hearing-loss) [ Antibiotic-free fixes for recurrent UTIs](https://www.health.harvard.edu/womens-health/antibiotic-free-fixes-for-recurrent-utis) [ Musculoskeletal syndrome of menopause: When menopause makes you ache all over](https://www.health.harvard.edu/womens-health/musculoskeletal-syndrome-of-menopause-when-menopause-makes-you-ache-all-over) [ When can older women stop getting mammograms?](https://www.health.harvard.edu/womens-health/when-can-older-women-stop-getting-mammograms) [ To lose weight, especially harmful belly fat, combine diet and exercise](https://www.health.harvard.edu/staying-healthy/to-lose-weight-especially-harmful-belly-fat-combine-diet-and-exercise) [ Can men hold off on treating recurring prostate cancer?](https://www.health.harvard.edu/blog/can-men-hold-off-on-treating-recurring-prostate-cancer-202512193108) [ The 7 types of rest and why we need them all](https://www.health.harvard.edu/mind-and-mood/the-7-types-of-rest-and-why-we-need-them-all) [ What are the early warning signs of cervical cancer?](https://www.health.harvard.edu/cancer/what-are-the-early-warning-signs-of-cervical-cancer) 1 / 10 ## Related Topics [ Diseases & Conditions CDC updates recommendations for pneumococcal and COVID vaccines](https://www.health.harvard.edu/diseases-and-conditions/cdc-updates-recommendations-for-pneumococcal-and-covid-vaccines) [ Staying Healthy Warding off germs this winter: What's helpful, what's not](https://www.health.harvard.edu/staying-healthy/warding-off-germs-this-winter-whats-helpful-whats-not) [ Diseases & Conditions The latest on long COVID](https://www.health.harvard.edu/diseases-and-conditions/the-latest-on-long-covid) [COVID-19](https://www.health.harvard.edu/topics/covid-19) [Infectious diseases](https://www.health.harvard.edu/topics/infectious-diseases) [Vaccinations](https://www.health.harvard.edu/topics/vaccinations) You might also be interested in…  ## COVID-19, Flu, and Colds: How to prevent and treat them — and spot the differences Any given year, we’ll collectively come down with one billion colds and up to 45 million cases of flu, while the number of new cases of COVID-19 keeps rising. In this guide you will learn how to avoid getting any of these three viral infections, and, if you do get sick, what you can do to feel better. You’ll also learn when your condition is serious enough to call a doctor. The report also provides specific information about high-risk groups for whom COVID and the flu can be very serious. [Read More](https://www.health.harvard.edu/diseases-and-conditions/covid-19-flu-and-colds?utm_source=site&utm_medium=web&utm_campaign=cross-sell) ## Free Healthbeat Signup Get the latest in health news delivered to your inbox\! 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 One reason people avoid getting a COVID booster is concern about side effects like fatigue, achiness, muscle and joint pain, chills, headache, and fever. But a new study found that these symptoms indicate a robust immune response to the vaccine that increases antibody levels and offers extra protection against the virus. Researchers examined the antibody responses and side effects from 363 people who had the two-dose Pfizer-BioNTech or Moderna mRNA vaccines. One month after the second dose, they found that those who cited at least one side effect, such as chills, fatigue, headache, or generally feeling unwell, had antibody levels 1.4 to 1.6 times higher than those who reported no symptoms. The researchers found that these levels were still elevated six months later. Of note, COVID vaccines increase antibody levels in almost everyone who gets vaccinated even if they have no symptoms. The study was published online June 10, 2024, by *Annals of Internal Medicine*. Smart strategies for achieving and maintaining a healthy weight  Successful weight loss depends largely on becoming more aware of your behaviors and starting to change them. Instead of relying on willpower, this process demands skill power. This Special Health Report, Lose Weight and Keep It Off, offers a range of solutions that have worked for many people and can be tailored to your needs. [Learn More\!](https://servedbyadbutler.com/redirect.spark?MID=186626&plid=2650436&setID=812675&channelID=0&CID=862911&banID=524318303&PID=0&textadID=0&tc=1&rnd=5115410464&scheduleID=3647184&adSize=0x0&matches=%5B%22healthy%22%5D&mt=1770424691068704&spr=1&referrer=https%3A%2F%2Fwww.health.harvard.edu%2Fstaying-healthy%2Fside-effects-after-a-covid-shot-indicate-its-working&request_uuid=b94f71c5-774f-448e-9e28-95a7dfc9e7ca&hc=7d4828dbb37523b8538837a11b71c31d762f209f&location=) **Image: © Jacob Wackerhausen/Getty Images**