Nearly half of participants in a recent study who were menstruating regularly at the time of the survey reported more intense bleeding during their periods after receiving the COVID-19 vaccine. Others who did not normally menstruate, including transgender men, people with long-acting contraceptives, and postmenopausal women, also experienced unusual bleeding.
The new study, the largest to date, expands research that has revealed the temporary effects of COVID-19 vaccines on menstrual cycles, but so far has focused primarily on menstruating cisgender women.
Although vaccines have largely prevented deaths and serious illnesses with few reported side effects, many medical experts initially put aside concerns when women and people of diverse genders began to report erratic menstrual cycles after receiving vaccinations.
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To get a better idea of these post-vaccination experiences, researchers at the University of Illinois at Urbana-Champaign and the University of Washington School of Medicine at St. Louis distributed an online survey in April 2021 to thousands of people around the world. After three months, the researchers collected and analyzed more than 39,000 responses from individuals between the ages of 18 and 80 about their menstrual cycles. All respondents had been completely vaccinated, with Pfizer-BioNTech, Moderna, Johnson & Johnson vaccines or one that had been approved outside the United States. And as far as they know, 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 more heavy bleeding after vaccination, while 44% reported no change and 14% reported lighter periods. In addition, 39% of respondents with gender-based hormone treatments, 71% of people with long-acting contraceptives, and 66% of postmenopausal women experienced intermittent bleeding after one or two injections.
The story goes on
“I think it’s important for people to know that this can happen, so they don’t get scared, they don’t get shocked, and they don’t get caught without supplies,” said Katharine Lee, a biological anthropologist at the School of Medicine. the University of Washington at St. Louis and the first author of the study.
Lee warned, however, that the study did not compare the results with a control group of people who were not vaccinated. And it is possible that people who observed changes in their cycles after vaccination were more likely to participate in the survey. However, the results are aligned with smaller studies that have reported menstrual changes after vaccination with stronger controls.
Importantly, the new study also found that some demographics may be more likely to experience menstrual changes and the study may help them be better prepared, Lee said. More intense menstrual flow was more likely for the elderly, for example. Survey respondents who used hormonal contraceptives, had been pregnant in the past, or had been diagnosed with a reproductive disease such as endometriosis, fibroids, or polycystic ovary syndrome were also more likely to have more severe bleeding. during their periods. People who identified as Hispanic or Latino tend to report more intense bleeding as well. And people who experienced other side effects from vaccines, such as fever or fatigue, were also more likely to suffer from irregular periods.
Postmenopausal women who were slightly younger, around an average age of 60, were more likely to experience intermittent bleeding after the vaccine than those who were older. But the type of vaccine postmenopausal women received, whether they had other side effects such as fever or a previous pregnancy did not appear to have any effect on their bleeding.
Why do these changes occur?
A certain level of variation in menstruation (the number of days you bleed, the heaviness of your flow, and the length of your cycle) is normal.
“Our menstrual cycles are not perfect clocks,” said Dr. Alison Edelman, a professor of obstetrics and gynecology at Oregon Health & Science University who has also studied the effect of COVID-19 vaccines on menstruation.
Hormones secreted by the hypothalamus, pituitary gland, and ovaries regulate the monthly cycle, and can be affected by both internal and external factors. Stress and illness, weight loss or gain, caloric restriction, and intense exercise can change typical menstrual patterns.
The endometrium, which covers the uterus and comes off during menstruation, has also been linked to the immune system. Because of the role it plays in remodeling uterine tissue and providing protection against pathogens, it is possible that when vaccines activate the immune system, which is what they should do, they also somehow trigger downstream effects in the endometrium, causing an alteration. in your menstrual cycle, Edelman said. And some people may be more sensitive to the immune or hormonal changes in their body.
In her research, Edelman found that some women’s periods came a day or two later than usual after getting vaccinated against the coronavirus. But the changes were temporary: menstruation tended to return to normal after one or two cycles.
What to do if you notice menstrual irregularities after the COVID vaccine
If you experience any new or unusual bleeding patterns, take note. The menstrual cycle can be seen as another vital sign, as can body temperature or blood pressure, which provides clues about your health, said Dr. Jennifer Kawwass, a reproductive endocrinologist at Emory University who did not participate. in the study.
“A significant change in menstrual cycle interval or bleeding profile justifies further research to ensure that there is no underlying endocrinological, hematological, or anatomical cause,” Kawwass said. Irruptive bleeding in people who no longer menstruate normally, for example, can also be a warning sign of cervical, ovarian, uterine, or vaginal cancer.
That said, subtle variation in your menstrual cycle, if you have regular periods, shouldn’t be a cause for concern and doesn’t require you to change anything you would normally do, Kawwass said.
Clinical trials and other studies have already established that COVID-19 vaccines are safe and effective and are unlikely to affect long-term fertility.
Do you need to get vaccinated at any point in your cycle?
Experts agree that the chaos that COVID-19 can cause throughout the body, including possible persistent effects, is far worse than any side effects caused by vaccination against the disease.
People who have previously had a fever after an injection can schedule their next dose on a day when they won’t have to go to work, Edelman said. But you shouldn’t let temporary menstrual changes stop you from getting vaccinated or strengthening yourself completely. As cases increase again, delaying vaccination for two weeks or more can significantly increase the risk of contracting COVID-19, he said.
However, it is important to monitor your body’s response to vaccination, and public health officials should acknowledge concerns about changes in the menstrual cycle as well as warn people of the risk of getting COVID-19. , said Keisha Ray, a bioethics expert at McGovern Medical School at UTHealth. Houston.
Increasing transparency around menstrual changes or other side effects of vaccination could also have another benefit: reducing people’s hesitation with the vaccine.
“We’re trying to be honest. We’re trying to validate people’s experiences,” Lee said. In turn, he hopes the new research will help improve conversations about people’s health and lead to more inclusive clinical trials in the future.
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