--- title: COVID-19 Vaccines Not Strongly Linked to Menstrual Changes description: The study is among the first to look at more severe bleeding events and changes in menstrual cycles after COVID-19 vaccination. canonical: https://time.com/6276989/covid-19-vaccine-period-changes/ author: Alice Park article:opinion: false article:content_tier: free article:published_time: 2023-05-04T14:43:34.000Z article:modified_time: 2026-08-04T07:51:14.519Z article:section: Health og:title: COVID-19 Vaccines Aren't Strongly Linked to Menstrual Changes, Study Says og:description: The study is among the first to look at more severe bleeding events and changes in menstrual cycles after vaccination og:url: https://time.com/6276989/covid-19-vaccine-period-changes/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltd1c1395cdc601035/698a3c8686f68e68376f2660/GettyImages-1303038502.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 2155 og:image:height: 1212 og:image:alt: covid-19-vaccination og:type: article twitter:card: summary_large_image twitter:title: COVID-19 Vaccines Aren't Strongly Linked to Menstrual Changes, Study Says twitter:description: The study is among the first to look at more severe bleeding events and changes in menstrual cycles after vaccination twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltd1c1395cdc601035/698a3c8686f68e68376f2660/GettyImages-1303038502.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # COVID-19 Vaccines Aren't Strongly Linked to Menstrual Changes, Study Says > Sponsored content. 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Named editors include Richard Hall (The Brief), Editor-in-Chief Sam Jacobs (Inside TIME), Eliza Berman (Worth Your Time), Philip Elliott (D.C. Brief), Justin Worland (Future Proof) and Harry Booth (In the Loop). Health Matters is written by TIME's health desk. #### How do I sign up for a TIME newsletter? Go to time.com/newsletters, choose the newsletters you want and enter your email address. There is no cost and no subscription requirement. ## Video: The Race to Make a Vaccine for Breast Cancer [Watch (HLS stream): The Race to Make a Vaccine for Breast Cancer](https://cdn.jwplayer.com/manifests/W5jcvwLu.m3u8) (8:09)  _Published 2022-10-05. Scientists believe there is a future in which women can be vaccinated against breast cancer._  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent May 4, 2023 2:43 PM UTC  Using a syringe to attack the new covid-19 variant. A young doctor in a white protective glove holds a medical syringe and a vial. Using a syringe to attack the new covid-19 variant. A young doctor in a white protective glove holds a medical syringe and a vial. Getty Images  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent May 4, 2023 2:43 PM UTC While the COVID-19 vaccines have made a dramatic difference in controlling the pandemic, researchers are still learning about the ways that the shots may affect people’s health. One of those questions centers around how the vaccines might impact menstrual cycles. [Reports](https://time.com/6217115/covid-19-vaccines-period-longer/) of women experiencing changes in their cycles—either in the intensity and frequency of bleeding, or the length of their periods—have prompted more rigorous investigations of how COVID-19 vaccines may be affecting cycles. In the latest [study](https://www.bmj.com/content/381/bmj-2023-074778), published in the _BMJ_, researchers led by Rickard Ljung, professor of epidemiology and physician specialist at the Swedish Medical Products Agency (the country’s equivalent to the U.S. Food and Drug Administration), looked at medical records from nearly 3 million Swedish women, ages 12 to 74\. They focused on those who had sought care from health care professionals for menstrual changes from Dec. 2020 to Feb. 2022 and were able to see when the women were vaccinated and how long after their immunization they sought care. That analysis found no strong association between COVID-19 vaccines and changes in menstruation—or at least bleeding events that were severe enough for women to seek medical care. --- ### More from TIME --- **Read More**: [_Why It’s So Hard to Have Your Fertility Tested_](https://time.com/6253707/fertility-testing-difficult/) The strongest association was among post-menopausal women. After a third dose (the booster) of either mRNA vaccine, made by Moderna or Pfizer-BioNTech, women had a 28% increased risk of bleeding in the first week after vaccination, and about a 25% increased risk of bleeding through the next three months, compared to before their vaccination. Ljung says that pattern doesn’t necessarily suggest an association between the two events, especially since a similar increase was not seen among premenopausal women. Ljung says that the association among post-menopausal women could be confounded by a number of factors, including the fact that they might be more attuned to bleeding events and more likely to see a physician than younger women, who may attribute any bleeding to irregular periods. Also, given that the data captured doctor’s visits, it’s unlikely that women would have been able to get an appointment with a physician within a week if they developed bleeding after getting vaccinated. “That’s a very short time to get that kind of appointment,” says Ljung. The pattern, he says, doesn’t support a possible causal connection between vaccination and changes in menstruation, and it’s likely the association seen among post-menopausal women might be reflecting other factors. The results don’t necessarily contradict the growing number of [reports](https://time.com/6198573/covid-19-vaccines-periods-mentrual-cycles/) of [changes in menstruation](https://time.com/6217115/covid-19-vaccines-period-longer/) following COVID-19 vaccination. Periods can be affected by any vaccine, but the current study shows that those changes might not be serious enough to require medical attention. “It’s a bit reassuring that there doesn’t seem to be an increased risk of more severe menstrual disturbances, bleeding, or other changes after vaccination,” says Ljung. Still, doctors don’t fully understand why immunization against COVID-19 could affect menstrual cycles, so more research is needed to appreciate how developing immunity against SARS-CoV-2 affects health. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/6276989/covid-19-vaccine-period-changes/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/6276989/covid-19-vaccine-period-changes/"},"headline":"COVID-19 Vaccines Aren't Strongly Linked to Menstrual Changes, Study Says","datePublished":"2023-05-04T14:43:34.000Z","dateModified":"2026-08-04T07:51:14.519Z","description":"The study is among the first to look at more severe bleeding events and changes in menstrual cycles after COVID-19 vaccination.","url":"https://time.com/6276989/covid-19-vaccine-period-changes/","keywords":["COVID-19","healthscienceclimate"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltd1c1395cdc601035/698a3c8686f68e68376f2660/GettyImages-1303038502.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Alice Park","jobTitle":"Senior Correspondent","url":"https://time.com/author/alice-park/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltd1c1395cdc601035/698a3c8686f68e68376f2660/GettyImages-1303038502.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"covid-19-vaccination","caption":"covid-19-vaccination","creditText":"Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/covid-19/","name":"COVID-19"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/6276989/covid-19-vaccine-period-changes/","name":"COVID-19 Vaccines Aren't Strongly Linked to Menstrual Changes, Study Says"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"The Race to Make a Vaccine for Breast Cancer","description":"Scientists believe there is a future in which women can be vaccinated against breast cancer.","thumbnailUrl":"https://cdn.jwplayer.com/v2/media/W5jcvwLu/poster.jpg?width=720","uploadDate":"2022-10-05T20:44:13.000Z","contentUrl":"https://cdn.jwplayer.com/manifests/W5jcvwLu.m3u8","embedUrl":"https://time.com/6276989/covid-19-vaccine-period-changes/","duration":"PT8M9S","potentialAction":{"@type":"SeekToAction","target":"https://time.com/6276989/covid-19-vaccine-period-changes/?jw_start={seek_to_second_number}","startOffset-input":"required name=seek_to_second_number"}}] ```