The Covid vaccine increased menstrual bleeding in 42% of women

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The largest study to date with more than

- women and people with gender diversity - has confirmed that

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

in a high number of people who did not have menstruation -because they had

or because they were following

or for gender change-, after receiving the vaccine against SARS-CoV-2.

The conclusions of this study, published this Friday in the journal Science Advances, confirm 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

and are associated with certain triggering factors such as age, suffering 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 reporting unexpected bleeding after being given the vaccine in early 2021," said US researchers and study leaders Katharine Lee of Tulane University and Kathryn Clancy of the University of Illinois Urbana-Champaign.

In vaccine trials, menstrual cycles or bleeding are not usually asked about, so this side effect is often ignored or ruled out of studies, despite the fact that

, 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

(because the disease can cause menstrual changes) and excluded data from people between 45 and 55 years of age to prevent the results from being confused with menopause or changes previous.

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

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

were the most likely to report heavier bleeding after vaccination, with a slight increase among those who had not given birth.

And more than 70% of respondents using

long-acting reversible

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 is why "this screening is very important to be able to detect cancers in time," says Clancy.

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

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