A study confirms that the COVID vaccine increased menstrual bleeding in 42% of women

The largest study to date with more than 35,000 participants -women and people with gender diversity- has confirmed that 42% of women experienced an increase in menstrual bleeding in the two weeks after being vaccinated against COVID.

In addition, the study describes for the first time the occurrence of spontaneous bleeding in a high number of people who did not have menstruation -because they had menopause or because they were following hormonal contraceptive treatment or for gender change-, after receiving the SARS-CoV-2 vaccine.

The conclusions of this study, published this Friday in the journal Science Advancesconfirm a side effect that had been reported by women and ignored by science and reveal that this effect of the vaccine has affected “a significant number of people.”

However, the study data show that these alterations are temporary and are associated with certain triggers such as agesuffering from systemic secondary effects associated with the vaccine (fever or fatigue), or history of pregnancies and childbirth, among others.

“Menstruating and previously menstruating people began to report experiencing a unexpected bleeding after they were given the vaccine in early 2021,” say North American researchers and study leaders Katharine Lee of Tulane University and Kathryn Clancy of the University of Illinois Urbana-Champaign.

Vaccine trials do not usually ask about menstrual cycles or hemorrhages, so this side effect is often ignored or ruled out of studies, despite the fact that some vaccines, such as those for typhoid fever, hepatitis B and HPV, can alter menstruation. To do the study, the authors used a survey asking people about their experiences after receiving the COVID vaccine.

The authors only included data from people who had not had COVID (because the disease can cause menstrual changes) and excluded data from people aged 45 to 55 years to avoid confounding results with menopause or previous changes.

Thus, the study focused on people with menstruation, menopausal women and people with hormonal therapies that suppress the cycle. 42.1% of the respondents said that they had a heavier menstrual flow in the first two weeks after vaccination, 43.6% that their menstrual flow had not changed and 14.3% had not experienced any change or , if anything, less bleeding than usual.

The study detected possible associations with reproductive history, hormonal status, demographics and changes in a person’s menstruation after vaccination. For example, respondents who had been pregnant were the most likely to report heavier bleeding after vaccination, with a slight increase among those who had not given birth.

Y more than 70% of respondents using long-acting reversible contraceptives and 38.5% of those undergoing gender-affirming hormone treatments reported this side effect. Although menstrual disturbances are not uncommon or dangerous, unexpected changes can be cause for concern.

“Unexpected intermittent bleeding is one of the first signs of some cancers in postmenopausal people and those using gender-affirming hormones,” Lee explains. That’s why “this screening is very important to be able to detect cancers early,” says Clancy.

The authors, however, reiterate that getting vaccinated is one of the best ways to prevent COVIDhospitalization, and death.