From the start of the Emergency Use Authorization (EUA) vaccines rollout, many women around the world have expressed concerns about the effects of COVID-19 vaccines on the female reproductive system.1 Recently, women in the United States have reported changes in their menstrual cycles after getting an EUA COVID-19 vaccine.2 3 4
Clinical Trials Did not Study COVID-19 Vaccine Effects on Women’s Reproductive Systems
Women experiencing menstrual cycle irregularities have taken to social media platforms to discuss what has happened to them following one or two doses of the COVID-19 vaccine, raising questions about the vaccines’ safety. Clinical trials of experimental COVID-19 vaccines did not evaluate the effects on women’s reproductive health prior to the U.S. Food and Drug Administration granting a EUA to Pfizer and Moderna in December 2020 to distribute experimental mRNA Covid-19 vaccines in the U.S.
So far, there have been few official responses from the scientific community to the reports of menstrual cycle disruption following COVID-19 vaccinations due to lack of studies published in the medical literature,5 However, reportedly there are researchers at several universities now looking into the adverse event reports from women concerned about fertility and health of their reproductive systems.6 In the meantime, most physicians continue to express confidence in COVID-19 safety and urge women to get vaccinated.7
Some of the reports on social media include women experiencing menstruation earlier than expected, absent periods, longer periods, painful menstrual cycles, heavy bleeding with clots, bleeding in women who are post-menopausal and menstrual irregularities in women taking hormonal birth control prescriptions.8
Many vaccinated women experiencing irregularities in their menstrual cycles did not immediately associate it with the COVID-19 vaccine. Katy Fyksen had unusually heavy menstruation a few days after she received her second dose of the Moderna COVID-19 vaccine but did not make an immediate connection to the vaccine she had recently received.9
A 43-year-old woman, who had not had a menstrual cycle in over a year and a half due to an intrauterine device (IUD) that prevents menstruation, suddenly experienced vaginal bleeding after vaccination. She said, “I didn’t really think that it was anything until I saw that someone had said that, that it might’ve been a symptom or a side effect of the vaccine. It was like, ‘Oh, that’s interesting’”10
Scientists Speculate About COVID-19 Vaccine-Induced Inflammation and Menstrual Irregularities
In response to the reports of women experiencing unusual menstruation cycle changes, scientists and physicians have said that there is not enough scientific evidence to show that the COVID-19 vaccine itself impacts menstruation; however, experts are proposing biological mechanism hypotheses to explain why and how the vaccines could be affecting menstruation.11
Akshat Jain, MD, a hematologist at Loma Linda University School of Medicine offered his incite stating:
Inflammatory reaction has been noticed with the COVID vaccine. We know that because many, including myself after the second vaccine, developed some mild flu like symptoms. That inflammation, has a potential or potentially can modulate estrogen response, which could be the link between certain women having heavy periods after the vaccine.”12
While scientists investigate, Dr. Jain recommends that women who experience heavy abnormal bleeding should seek medical attention from their doctor to get a blood count and estrogen test.13
Obstetrician Comments on Knowledge Gaps in Clinical Trials of COVID-19 Vaccines
Heather Huddleston, MD, an obstetrician-gynecologist (OB-GYN) that specializes in reproductive endocrinology at University of California, San Francisco says that vaccine makers should have collected data about menstrual cycles during the randomized trials.14 She states:
There’s a long history of us not doing a great job at studying women in research studies because of some of this complexity The train sort of left the station on that because we are now recommending the vaccine for everybody. So it will be very hard for us to generate a control group to answer this question.15
Scientists Study the Association Between COVID-19 Vaccines and Menstruation
Two scientists working at Washington University and University of Illinois, who themselves experienced irregular menstrual cycles following COVID-19 vaccination, decided that the issue deserved more attention and began collecting and examining anecdotal data on women’s menstruation experiences after COVID-19 vaccination with the aim of facilitating further research.16
None of the clinical trials for the COVID-19 vaccines being distributed in the U.S. under an EUA examined changes in menstruation as a potential adverse effect.17 The U.S. Centers for Disease Control and Prevention (CDC) does not list it as a potential side effect of the vaccine either.18
Katharine Lee, PhD, a postdoctoral scholar in the Washington University School of Medicine Division of Public Health Sciences and her dissertation advisor Kate Clancy, PhD, an associate professor of Anthropology at the University of Illinois in Urbana-Champaign, who has studied menstruation in different contexts, designed an exploratory survey to collect data on women’s menstruation experiences after COVID-19 vaccination.19
Any menstruating or formerly menstruating woman, regardless of whether they had any irregularities, can sign up and report what they experience following any dose of any of the vaccines. Over 13,000 women have responded to the survey.20
Dr. Lee said:
If this isn’t something that’s specifically asked about, then people aren’t going to think to report it necessarily. It does seem like it should be part of the standard set of questions we ask when we’re testing vaccines in healthy adults. For me, it comes down to making sure that people who might experience menstrual bleeding after the vaccine know that it might occur after the vaccine, especially if they are perimenopausal or on hormone suppressing medication.21
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Click here to view References:
1 News Staff. Can the COVID-19 vaccine affect women’s menstrual cycles? Here’s what we know. WSOCTV May. 3, 2021.
2 Miller K. Can the COVID Vaccine Affect Your Period? Some Women Say It’s Changed Theirs – Here’s what We Know Right Now. Health Apr. 6, 2021.
3 Stern C. Women say they are having heavier and more painful PERIODS since getting their COVID-19 vaccines – as several claim it has also messed up their monthly cycle. Daily Mail Apr. 7, 2021.
4 Matsuzawa S. Can the COVID-19 vaccine cause changes in a woman’s menstrual cycle? KTVB May. 2, 2021.
5 Amitage M. Is the COVID-19 Vaccine Affecting My Period? GoodRX Apr. 29, 2021.
6 Associated Press. Researchers Studying whether COVID-19 vaccines affect women’s periods after anecdotal reports of irregular bleeding. KTLA May 7, 2021.
7 Larsen K. Reports of menstrual cycle changes after COVID vaccine highlight issues with clinical trials. ABC7 News.com Apr. 28, 2021.
8 Cox C. There’s no solid evidence COVID-19 vaccines cause menstrual cycle changes. That doesn’t mean it’s impossible. Insider Apr. 21, 2021.
9 Stock N. Some people are reporting abnormal periods after a COVID-19 vaccine. U. of I. professor is looking for answers. Chicago Tribune Apr. 20, 2021.
11 Cox C. There’s no solid evidence COVID-19 vaccines cause menstrual cycle changes. That doesn’t mean it’s impossible. Insider Apr. 21, 2021.
12 Larsen K. Reports of menstrual cycle changes after COVID vaccine highlight issues with clinical trials. ABC7 News Apr. 28, 2021.
16 Haelle T. Lack of Data on Covid-19 Vaccines and Periods Inspired Two Feminist Scientists to Learn More. Elemental.Medium Apr. 13, 2021.
18 U.S. Centers for Disease Control & Prevention. Possible Side Effects After Getting a COVID-19 Vaccine. Mar. 16, 2021.
19 Haelle T. Lack of Data on Covid-19 Vaccines and Periods Inspired Two Feminist Scientists to Learn More. Elemental.Medium Apr. 13, 2021.