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Researchers to Study How the Vaccine Affects Menstrual Cycles


If you experienced changes to your period after getting vaccinated, you’re not alone. Many women have reported similar experiences, but there’s still a lot we don’t know in terms of whether the COVID-19 vaccine can affect menstrual cycles. 

Several organizations are coming together to research the mysterious trend, so scientists can prevent it from happening in the future.

Anecdotal Evidence

Like many in the medical community, Katharine Lee was one of the first people to get vaccinated against the coronavirus in the U.S. She works as an anthropologist at Washington University School of Medicine in St. Louis, MO. 

“I was on the earlier end of getting vaccinated,” she said. Lee was concerned about possible side-effects, including fever, fatigue, and muscle aches, but the vaccine affected her in surprising ways.

“I’m on the Mirena IUD, so I normally don’t experience a period. And so, I had breakthrough bleeding and cramping, which for me is really, really unusual,” she said. Lee added that the bleeding was spotting and not serious, just uncomfortable.

She reached out to one of her colleagues, Kate Clancy, an anthropologist at the University of Illinois, to see if she had heard of anyone experiencing something similar. Clancy used her large following on Twitter to ask just that. She was soon flooded with responses from women from all over the country.

“I just decided to ask, and I did not anticipate it blowing up to the extent that it has,” Clancy said. “A lot of emails, a lot of Instagram DMs and a lot of tweets of people who are, like, just baring their souls to us.”

Clancy and Lee put together a survey to report these symptoms. They already have over 140,000 signatures with most women reporting heavier than usual flows and some breakthrough bleeding among different types of people.

“We started hearing a lot about breakthrough bleeding from people on long-acting, reversible contraception, people on gender-affirming hormones and postmenopausal people who were years and years out from their last period, sometimes decades out,” Clancy explained.

Lee clarified that this represents a small percentage of those that get vaccinated.

“It’s not going to be representative of the averages of everyone who’s vaccinated,” she said.

Finding a Link

Lee and Clancy’s work points to a clear gap in research on the topic.

The FDA and all three U.S. vaccine manufacturers say they haven’t seen any noticeable changes in menstruation following vaccination and that the vaccines are safe and effective. There is no known link between the COVID-19 and changes in a person’s menstrual cycle and all evidence remains anecdotal.

However, there are no published scientific studies on the topic. But now the medical community says it plans to investigate the issue further.

Dr. Hugh Taylor, chair of the department of obstetrics, gynecology and reproductive sciences at Yale School of Medicine, said he has heard comments from his patients regarding changes in menstruation.

“This is an important, overlooked issue,” he said. “A lot of people have irregular menstruation for all sorts of reasons, so is this really different in people with the vaccine, or is it just that when people have it, they are linking it to the vaccine?”

Researchers at Boston University, Harvard Medical School, Johns Hopkins University, Michigan State University and Oregon Health and Science University recently announced they are collaborating on a project that will study the menstrual cycles of people of all ages and backgrounds, including those that have yet to get vaccinated and those that plan on getting their shots, so they can compare the results.

Experts say while this issue is important, there’s no reason to worry. Kathryn Edwards, a physician at Vanderbilt University who also sits on an independent monitoring committee for the Pfizer vaccine, said, “We haven’t really heard much concern about menstrual issues. If it were leading to hospitalizations and severe illness, we would catch that.”

However, Edwards points out that most clinical trials often look for common symptoms related to the virus and vaccines, such as headaches, fever, and muscle aches. They rarely include questions about a person’s menstrual cycle.

“There aren’t any queries to say, are your menstrual periods irregular? You know, are you – is your flow heavier?” she said.

Researchers at the FDA say they are going back through data from the clinical trials to see if there were any minor menstrual changes they may have missed.

Menstruation can represent a woman’s overall health, but it’s hard to know whether these changes are related to the vaccine. We’ve all experienced our fair share of stress and lifestyle changes over the years related to the pandemic.

Laura Riley, doctor and chief of obstetrics and gynecology at New York-Presbyterian Weill Cornell Medical Center, says this data shouldn’t prevent anyone from getting vaccinated.

“You need to get vaccinated. The effects of getting COVID-19, especially with rising cases due to this variant, are so much worse than missing a period or having one or two that are heavy,” she said.

However, she says patients have a right to ask questions about possible menstrual changes. She encourages providers to have an open conversation about these side-effects, even if they remain rare.

“We need to do a better job of being able to answer those questions because when you can’t answer the questions, you’re asking people just to believe, and that’s not a thing,” Riley added.

Steven Briggs
Steven Briggs is a healthcare writer for Scrubs Magazine, hailing from Brooklyn, NY. With both of his parents working in the healthcare industry, Steven writes about the various issues and concerns facing the industry today.

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