Covid-19 vaccines temporarily altered menstrual cycles, study finds

Almost half of participants in a recent study who menstruated regularly at the time of the survey reported heavier bleeding during their periods after receiving the Covid-19 vaccine. 19. Other people who usually missed their periods, including transgender men, people taking long-acting contraceptives, and postmenopausal women, also experienced unusual bleeding.

The new study, the largest to date - expands research that has highlighted the temporary effects of Covid-19 vaccines on menstrual cycles, but has so far focused primarily on cisgender women who have their rules.

Although vaccines have largely prevented death and serious illness with few reported side effects, many medical experts initially dismissed concerns when women and gender-diverse people began to report irregular menstrual cycles after receiving the injections.

look for Researchers at the University of Illinois at Urbana-Champaign and Washington University School of Medicine in St. Louis distributed an online survey in April 2021 to thousands of people across the globe. After three months, the researchers collected and analyzed more than 39,000 responses from people between the ages of 18 and 80 regarding their menstrual cycles. All of the survey respondents had been fully immunized — with Pfizer-BioNTech, Moderna, Johnson & Johnson, or another that had been approved outside the United States. And to their knowledge, the participants had not contracted Covid-19 before being vaccinated.

The research, published Friday in the journal Science Advances, shows that 42% of people with regular menstrual cycles experienced heavier bleeding after vaccination, while 44% reported no change and 14% reported lighter periods. Additionally, 39% of respondents on gender-affirming hormone therapy, 71% of people on long-acting contraceptives, and 66% of postmenopausal women experienced breakthrough bleeding after one or both injections.

"I think it's important for people to know this can happen, so they don't get scared and shocked and don't not be taken without supplies," said Katharine Lee, a biological anthropologist at Washington University School. of Medicine in St. Louis, and the study's first author.

Dr. Lee cautioned, however, that the study did not compare the results with a control group of people who were not vaccinated. And it's possible that people who observed changes in their cycles after vaccination were more likely to participate in the survey. Yet the results are consistent with smaller studies that have reported menstrual changes after vaccination with more robust controls.

It is important to note that the new study has also revealed that certain demographics may be more likely to experience menstrual changes, and the study may help them be better prepared, Dr. Lee said. A heavier menstrual flow was more likely for those who were older, for example. Survey respondents who used hormonal contraception, had been pregnant in the past, or had been diagnosed with a reproductive condition such as endometriosis, fibroids, or polycystic ovary syndrome were also more likely to have heavier bleeding. during their period. People who identified as Hispanic or Latino also tended to report heavier bleeding. And people who experienced other vaccine side effects, such as fever or fatigue, were also more likely to have irregular periods.