Well-Being Medical Advances

Thousands report changes to menstrual bleeding after COVID-19 vaccine, study shows

Many women and menstruating people reported heavier bleeding after getting the jab.
FILE – A syringe is prepared with the Pfizer COVID-19 vaccine at a vaccination clinic at the Keystone First Wellness Center in Chester, Pa., Dec. 15, 2021. Pfizer says tweaking its COVID-19 vaccine to better target the omicron variant is safe and boosts protection. Saturday, June 25, 2022 announcement comes just days before regulators debate whether to offer Americans updated booster shots this fall. (AP Photo/Matt Rourke, File)

Story at a glance


  • A new study published in the journal Science Advances offers one of the most comprehensive looks at menstrual changes post COVID-19 vaccine.  

  • Two researchers, Kathryn Clancy and Katharine Lee, led the effort to study reported changes in menstrual bleeding in people who have been vaccinated against the virus.  

  • Over 40 percent of survey respondents used for the study reported heavier bleeding within two weeks of getting the jab.  

The COVID-19 vaccine temporarily impacted women and menstruating people’s periods, a new study suggests.  

Reports of people experiencing changes to their menstrual cycles after receiving a COVID-19 vaccine started popping up in 2021. But little research had been done to assess the connection and all three COVID-19 vaccine manufactures denied any link between the inoculation and changes in menstrual bleeding or fertility.  

Two researchers, Kathryn Clancy who is an associate professor of anthropology at the University of Illinois Urbana-Champaign and Katharine Lee, an anthropology professor at Tulane University, wanted to fill that gap in knowledge.

 


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To do that the two launched an online survey last year to investigate the recently vaccinated’s menstrual experience post jab. After the survey closed, the pair analyzed the accounts of over 39,000 pre- and post-menopausal people who responded.  

The result of that analysis was published earlier this month in the journal Science Advances and offers one of the largest looks at a potential link between the vaccine and changes to menstrual bleeding.  

Out of the survey’s respondents, just over 42 percent reported experiencing heavier menstrual bleeding in the two weeks after receiving a COVID-19 vaccine, the study shows.  

Some reported noticing a heavier flow within seven days of getting the jab but most spotted changes in between day 8 and day 14 post vaccination.  

Meanwhile, roughly the same amount of respondents —just over 43 percent — said they experienced no change in menstrual bleeding after getting the shot. While a small pool of people, roughly 14 percent, reported a mix of either no change or lighter flow, according to the study.  

The COVID-19 vaccine is not unique in its reported impact on menstrual cycles. Changes to menstrual cycles in recipients of vaccines for typhoid, Hepatitis B and the Human Papillomavirus have been documented.  

“Any agent that triggers an immune response could plausibly influence cellular processes in the uterus and ovaries that could have an impact on menstruation,” said Taraneh Shirazian, an associate professor and director of the division of global and community women’s health at NYU Langone Health’s department of obstetrics and gynecology, who did not take part in the study.  

“This doesn’t have any long-term consequences but getting COVID disease will likely disrupt the menstrual cycle much more than the vaccine.”  

Shirazian found the rate of break-through bleeding in typically non-menstruating people to be interesting.  

Among survey respondents, 71 percent of people on long-acting reversable birth control, 39 percent of people on gender-affirming hormones and 66 percent of post menopausal people reported breakthrough bleeding within two weeks of getting vaccinated.  

“This might support the idea that spotting with the vaccine is not associated with fertility and the spotting is just a result of a new ‘stress’ on the reproductive system,” Shirazian told Changing America.  

Both Lee and Clancy agree that vaccine-related changes to menstrual cycles are likely associated with “immune-related inflammatory pathways” and not hormonal changes.  

Since the survey relied on self-reported responses to the vaccine, the study cannot cement causality or predict the vaccine’s effect on menstruating people, Lee said.  

But it does add to the existing research on the potential link between the COVID-19 vaccine and changes to a person’s menstrual flow as well as reproductive history, hormonal status and demographics.  

 “We’d love to see future vaccine testing protocols incorporate questions about menstruation that go beyond screening for pregnancy,” Lee said. “Menstruation is a regular process that responds to all kinds of immune and energetic stressors, and people notice changes to their bleeding patterns, yet we don’t tend to talk about it publicly.” 


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