Largest study to date shows how COVID vaccines affect periods

Nearly half of the participants in a recent study, who were menstruating regularly at the time of the survey, reported heavy bleeding during their periods after receiving the COVID-19 vaccine. Others who did not menstruate – including transgender men, people taking long-acting contraceptives and postmenopausal women – also experienced unusual bleeding.

The new study – the largest to date – expands on research that has highlighted the temporary effects of COVID-19 vaccines on menstrual cycles, but so far it has focused primarily on menstruating women.

Although the vaccines largely prevented deaths and severe disease with few reported side effects, many medical experts initially ignored the concerns when women and people of variety began to report irregular menstrual cycles after receiving the injections.

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To get a better idea of ​​these post-vaccination trials, researchers at the University of Illinois at Urbana-Champaign and Washington University School of Medicine in St. Lewis distributed an online survey in April 2021 to thousands of people around the world. Three months later, the researchers collected and analyzed more than 39,000 responses from individuals between the ages of 18 and 80 about their menstrual cycles. All survey participants were fully vaccinated – with the Pfizer-BioNTech, Moderna and Johnson & Johnson vaccines, or with other vaccines approved outside the United States. To their knowledge, participants did not have COVID-19 prior to vaccination.

The research, published Friday in Science Advances, showed that 42% of people with regular periods experienced heavy bleeding after the vaccination, while 44% reported no change, and 14% reported having a lighter period. Additionally, 39% of respondents on sex-confirmed hormone treatments, 71% of people taking long-acting contraceptives and 66% of postmenopausal women experienced sudden bleeding after one or both shots.

“I think it’s important for people to know that this can happen, so they are not afraid, they are not shocked, and they are not caught without a supply,” said Catherine Lee, a biological anthropologist at the University of Washington School of Medicine. Street. Lewis and first author of the study.

However, Lee cautioned, the study did not compare results to a control group of people who were not vaccinated. It is possible that people who notice changes in their cycles after vaccination may be more likely to participate in the survey. However, the results are in line with smaller studies reporting menstrual cycle changes after vaccination with more robust controls.

Importantly, the new study also found that certain demographics may be more susceptible to menstrual cycle changes, and the study may help them prepare better, Lee said. Heavy menstrual flow was more likely for those who were older, for example. Survey participants who had 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 more likely to have more profuse bleeding during their periods. People who are identified as Hispanic or Hispanic tend to report heavy bleeding as well. And people who experienced other side effects of vaccines, such as fever or fatigue, also had a higher chance of experiencing irregular periods.

Slightly younger postmenopausal women, with a mean age of 60 years, were more likely to have breakthrough bleeding after vaccination than older women. But the type of vaccine post-menopausal women received, whether they had other side effects such as fever or whether they had a previous pregnancy, didn’t seem to have an effect on their bleeding.

Why did these changes occur?

A certain level of variability in the menstrual cycle — the number of bleeding days, the heaviness of the flow and the length of the cycle — is normal.

Dr. said. Alison Edelman, a professor of obstetrics and gynecology at Oregon Health & Science University who has also studied the effect of COVID-19 vaccines on the menstrual cycle.

The hormones secreted by the hypothalamus, pituitary gland, and ovaries regulate the menstrual cycle, and can be influenced by both internal and external factors. Stress and illness, weight loss or weight gain, calorie restriction, and intense exercise can alter normal menstrual patterns.

The endometrium, which lines the uterus and sheds during menstruation, has also been linked to the immune system. Because of the role they play in remodeling uterine tissue and providing protection against pathogens, it’s possible that when vaccines activate the immune system, which they should, they somehow trigger bloodstream effects in the endometrium, causing the disruption. Your period, Edelman said. Some individuals may be more sensitive to immune or hormonal changes in their bodies.

In her research, Edelman found that some women come a day or two later than usual after receiving a coronavirus vaccination. But the changes were temporary – menstruation tended to return to normal after one or two cycles.

What to do if you notice irregular periods after the COVID vaccine

If you experience any new or unusual patterns of bleeding, write this down. Dr. said. Jennifer Coase, a reproductive endocrinologist at Emory University, who was not involved in the study.

“A significant change in menstrual period or bleeding profile warrants further investigation to ensure that there is no underlying cause related to the endocrine, hematological, or anatomical,” Kawas said. For example, breakthrough bleeding in people who no longer menstruate may be a warning sign of cancer of the cervix, ovaries, uterus, or vagina.

However, the slight difference in your menstrual cycle, if you have regular periods, should not be a cause for concern and does not require you to change anything you normally do.

Clinical trials and other studies have already demonstrated that COVID-19 vaccines are safe and effective and are unlikely to affect fertility in the long term.

Should you get the vaccination at a certain time of your cycle?

Experts agree that the havoc that COVID-19 can wreak throughout the body, including the potential residual effects, are far worse than any side effects from a vaccination against the disease.

Edelman said that people who previously had a fever after a shot may plan their next dose on a day when they don’t have to go to work. But you shouldn’t let menstrual changes prevent you from getting a full vaccination or booster. She said that because cases are again on the rise, delaying vaccination for two weeks or more could significantly increase the risk of contracting COVID-19.

Still, it’s important to track your body’s response to vaccination, and public health officials should acknowledge concerns about menstrual fluctuations as well as warn people about the risk of COVID-19, said Keisha Ray, a bioethicist at UTHealth’s McGovern School of Medicine. Houston.

Increased transparency about menstrual changes or other side effects of vaccination could have another benefit: reducing people’s hesitation to get a vaccine.

“We’re trying to be honest. We’re trying to validate people’s experiences,” he told me. In turn, she hopes the new research will help improve conversations about people’s health and lead to more comprehensive clinical trials in the future.

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