Nearly half of the participants of a recent study who were menstruating regularly at the time of the survey reported heavier bleeding during their periods after receiving the Covid-19 vaccine. Others who did not typically menstruate — including transgender men, people on long-acting contraceptives, and post-menopausal women — also experienced unusual bleeding.
The new study — the largest to date — expands on research that has highlighted the temporary effects of Covid-19 vaccines on menstrual cycles, but until now focused primarily on cisgender women who menstruate.
Although the vaccines have 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.