Researchers think it’s finally time to add another common one to the list of COVID-19 vaccine side effects: temporary menstrual changes.
An analysis published Friday (July 15) in the journal Science Advances found that 42% of people with regular menstrual cycles said they bled more heavily than usual after vaccination. Meanwhile, 44% reported no change and around 14% reported a lighter period. Among non-menstruating women—those post-menopause or who use certain long-term contraceptives—the study suggests many experienced breakthrough or unexpected bleeding after their COVID-19 shots.
The new survey started in April 2021, around the time women began to report unexpected bleeding and heavier flow post-vaccine. However, these anecdotes were at the time met with the rebuttal that there was no data linking menstrual changes to vaccination.
Other recent research has also found that the COVID-19 vaccine is associated with a change in menstrual cycle length.
Women who took part in COVID-19 vaccine trials were not asked if they experienced menstrual changes.