Can COVID-19 vaccines affect menstruation?

A new study, published in the journal Science Advances, has found that Covid 19 vaccines affected menstruation cycles in women though there was no major cause for alarm.
Quoting the study, the New York Times reported that researchers from the University of Illinois at Urbana-Champaign and Washington University School of Medicine in St. Louis had found that 42 per cent of women experienced heavier bleeding during their menstrual cycle. Even in people who typically do not menstruate — 71 per cent of people on long-acting reversible contraceptives, 39 per cent of transgender males on gender-affirming hormones, and 66 per cent of post-menopausal women, reported breakthrough bleeding. The findings are a development in a relatively unknown field in medicine. The study was the largest one of its kind with researchers analysing more than 39,000 responses from an online survey with the participants ranging from 18 to 80. The individuals self-reported that they had not contracted the virus before getting the vaccine.
So what’s the logic? The bleeding could be a result of the vaccine’s ability to remodel uterine tissue and offer protection against pathogens. activating the immune system, the vaccine triggers downstream effects in the endometrium, durbing the menstrual cycle. And should you be more sensitive to immune or hormone changes in their body, you could manifest changes in your cycle. For example, the study found that some women’s periods came a day or two later than usual after they got vaccinated against the Coronavirus. But the changes were temporary — menstruation tended to return to normal after one or two cycles.
However, the study does have some limitations. “We don’t know the authenticity of the responses. We don’t know about the exact amount of bleeding except the fact that people just felt some difference,” says Dr Sarika Gupta, Senior Consultant of the Oncology and Robotic Gynaecology Department at Apollo Hospital, New Delhi. The study did not compare its results with an unvaccinated control group. Additionally, Dr Gupta says, “Only people who noticed changes in their menstrual cycles took the survey. The findings become less reliable.”Calling it “statically insignificant”, she added that “to say that the vaccination interfered with their cycles, we need very specific statical tests and a controlled randomised study.”
But the study did highlight which demographics are more prone to changes in their menstruation. Older individuals are likely to have heavier bleeding. The same goes for people who had been pregnant before, or with conditions like endometriosis and polycystic ovarian syndrome. Latino and Hispanics also reported heavier bleeding.
Specifically, post-menopausal women on the younger side also reported bleeding after the vaccine. “Post-menopausal spotting is very common. In patients who come to me, it is just a breakthrough bleeding. It is a benign thing which happens,” says Dr Gupta. Although, she warns, a small percentage of those with post-menopausal bleeding had cancer.
Hormones that are secreted the hypothalamus, pituitary gland and ovary control the menstrual cycle. However, they are very susceptible to internal or external factors.
According to Dr Gupta, the change in menstrual cycles is nothing to worry about. “Menstruation is very dynamic. Sometimes it is heavy and sometimes it is not. It also depends upon our physical activity and external environment. Just a little bit of stress can make a difference in the days and amount of bleeding.”
In most cases, the menstruation cycle goes back to normal quickly. However, if the changes keep continuing and growing, it is time to see your doctor.
The New York Times wrote that although the vaccines had largely prevented deaths and severe disease with few reported side effects, “many medical experts initially brushed aside concerns when women and gender-diverse people started reporting erratic menstrual cycles after receiving the shots. To get a better sense of these post-vaccination experiences, researchers at the University of Illinois at Urbana-Champaign and Washington University School of Medicine in St. Louis dributed an online survey in April 2021 to thousands of people across the globe. After three months, the researchers collected and analysed more than 39,000 responses from individuals between the ages of 18 and 80 about their menstrual cycles. All the survey respondents had been fully vaccinated — with the Pfizer-BioNTech, Moderna, Johnson & Johnson vaccines or another that had been approved outside the United States. And to the best of their knowledge, the participants had not contracted Covid-19 before getting vaccinated.”
“I think it’s important that people know this can happen, so they’re not scared, they’re not shocked and they’re not caught without supplies,” said Katharine Lee, a biological anthropolog at the Washington University School of Medicine in St Louis and the study’s first author.