Largest study to date finds alarming percentage of women experienced menstrual cycle changes after receiving COVID vaccines

A new study discovered that changes in menstrual cycles of women who received the COVID-19 vaccines are far more prevalent than previously acknowledged. The study found that 56% of women experienced changes in their menstrual cycle after being double-vaccinated against COVID.

Over 39,000 adults around the world, ages 18 to 80, who received two doses of the COVID vaccine participated in the study. The participants were vaccinated with Pfizer, Moderna, AstraZeneca, Johnson & Johnson, and Novavax vaccines.

An alarming 42% of study participants said they experienced heavier bleeding during their menstrual cycle after receiving the COVID vaccine.

There were 14% of participants who experienced unusually lighter menstrual cycles, and 44% who reported no change.

“In terms of who was more likely to see this effect in our sample … people who were Hispanic were more likely to see heavier bleeding,” said researcher and study author Katharine Lee, Ph.D. “People who were older in the pre-menopausal group were more likely to see heavier bleeding. (People) diagnosed with … something like endometriosis or fibroids were more likely to see heavy bleeding.”

Australia’s Nine News reported, “The researchers highlighted that many study participants observed the changes to their menstrual cycles more than a week after vaccination, which is beyond the period when adverse symptom reporting is closely monitored during trials for vaccine reactions.”

Science.org – a peer-reviewed academic journal – added, “In the survey results published today, 66% of 673 postmenopausal people reported breakthrough bleeding, as did 39% of the 280 people on gender-affirming hormones.”

However, there was a different message about vaccines affecting menstrual cycles earlier in the pandemic.

“So far, there’s no data linking the vaccines to changes in menstruation,” Alice Lu-Culligan and Dr. Randi Hutter Epstein at Yale School of Medicine wrote in the New York Times in April 2021. “Even if there is a connection, one unusual period is no cause for alarm.”

In May 2021, the San Francisco Chronicle called “claims that vaccines may affect women’s menstrual cycles” are “myths and misinformation.”

In January 2022, the National Institutes of Health (NIH) assured Americans: “COVID-19 vaccines linked to small increase in menstrual cycle length.”

The Centers for Disease Control and Prevention (CDC) does not list changes in the menstrual cycle as one of the “possible side effects after getting a COVID-19 vaccine.”

The Science journal noted, “Clinical trials of COVID-19 vaccines didn’t look for effects on the menstrual cycle.”

Lee claimed that menstruation is ignored by science because “there are very few senior people in science and medicine who are not white men. It’s just not something they are thinking about as part of their lived experience.”

“Generally, changes to menstrual bleeding are not uncommon or dangerous, yet attention to these experiences is necessary to build trust in medicine,” the authors of the study wrote in the journal Science Advances.