COVID vaccine recipients report changes in menstrual bleeding - study

42% of the nearly 40,000 respondents reported heavier bleeding than usual during their menstrual cycles in the first three months after being vaccinated.

 Prepping the vaccine at a Health Ministry center in Jerusalem's Malcha Mall (photo credit: OLIVIER FITOUSSI/FLASH90)
Prepping the vaccine at a Health Ministry center in Jerusalem's Malcha Mall
(photo credit: OLIVIER FITOUSSI/FLASH90)

A study found that 42% of respondents reported heavier bleeding than usual during their menstrual cycles after being inoculated with the COVID-19 vaccine.

In this study, which was published in the peer-reviewed scientific journal Science Advances, researchers surveyed nearly 40,000 women who had received their COVID vaccine schedule and found that 42% reported heavier bleeding than usual within the first three months after being vaccinated.

While 44% of respondents reported no changes, there were also changes reported among women who do not menstruate – 71% of people on long-acting reversible contraceptives, 39% of people on gender-affirming hormones, and 66% of postmenopausal women reported breakthrough bleeding. 

Further, 14.3% of respondents saw a mix of no change or lighter flow, the researchers report.

 A woman suffers stomach pains or cramps (Illustrative) (credit: FLICKR) A woman suffers stomach pains or cramps (Illustrative) (credit: FLICKR)

Menstrual activity and vaccines

The COVID vaccine is not the first to result in irregular menstrual cycles for those inoculated – a 1913 study cited in the research found that the typhoid vaccine was associated with menstrual irregularities – including irregular menstruation, discomfort; and heavy bleeding in more than half of the female sample studied. Hepatitis B and HPV (human papillomavirus) vaccines also resulted in irregular menstrual cycles.

"We suspect that for most people the changes associated with COVID-19 vaccination are short-term, and we encourage anyone who is worried to contact their doctor for further care,” one of the researchers said. “We want to reiterate that getting the vaccine is one of the best ways to prevent getting very sick with COVID, and we know that having COVID itself can lead not only to changes in periods but also hospitalization, long COVID and death.”