A new study published in the American Association for the Advancement of Science journal "Science Advances" reveals the risk of unexpected vaginal bleeding after covid vaccination, even in non-menstruating women.
The study, conducted by the Norwegian Institute of Public Health, followed several cohorts of women throughout the pandemic, and collected self-reported data on unexpected vaginal bleeding in non-menstruating women. A total of 21,925 non-menstruating women were represented in the study.
The results found that 3.3% of postmenopausal women (n=7,720; median age 56), 14.1% of perimenopausal women (n=7,148; median age 52) and 13.1% of premenopausal women (n=7,052; median age 45) experienced unexpected vaginal bleeding during a period of 8 to 9 months post vaccination.
In postmenopausal women, the risk of unexpected vaginal bleeding in the 4 weeks after COVID-19 vaccination was increased two- to threefold, compared to the pre-vaccination period. It should be noted that postmenopausal vaginal bleeding can be a sign of endometrial carcinoma and precancerous lesions, and should be considered an important medical event.
The risk of unexpected vaginal bleeding after vaccination was increased three- to fivefold in both non-menstruating perimenopausal and premenopausal women.
Furthermore, in the premenopausal women, Moderna's Spikevax was associated with a 32% increased risk as compared to Pfizer's Comirnaty.
This is not the first study to find a relationship between covid vaccination and unexpected menstrual bleeding. Other studies have reported even higher frequencies of unexpected bleeding after covid shots than this one, including a June 2023 study that found that 11.1% and 37.5% of post-menopausal women reported menstrual symptoms after the first and second dose cycles, respectively.
Additionally, a July 2022 study revealed that 42% of people with regular menstrual cycles bled more heavily than usual post covid shots. Among respondents who typically do not menstruate, 71% of people on long-acting reversible contraceptives and 66% of postmenopausal people reported breakthrough bleeding.
It's no wonder the European Medicines Agency recently decided that the Spikevax and Comirnaty package inserts should be updated to reflect heavy menstrual bleeding as a possible side effect.