An American study, published on January 5, shows that the menstrual cycle of some women can be lengthened by almost a day after vaccination against Covid-19. A mild side effect, according to the researchers. Especially since the duration of the rules is not modified.
Vaccinated versus unvaccinated women
A large study, published in the journal Obstetrics & Gynecology, wanted to check whether the Covid vaccines disrupted the menstrual cycle. Researchers at Oregon Health & Science University studied six consecutive menstrual cycles in 2,400 women aged 18 to 45. They were all vaccinated against the coronavirus with Pfizer (55%), Moderna (35%) and Johnson & Johnson (7%). These women were not taking contraceptives. The results were compared to 1,500 unvaccinated women.
Minimal lengthening of the cycle
A lengthening of the menstrual cycle, that is to say the period between each start of menstruation, has been observed in vaccinated women. A gap of 0.64 more days in the cycle after the first dose of vaccine and 0.79 after the second. Still, study lead author Alison Edelman stressed that any change in cycle length of less than eight days is considered normal.
“The immune and reproductive systems are interconnected”,
Many women have reported changes in their cycles following their vaccination. For Alison Edelman, nothing abnormal since “the immune and reproductive systems are interconnected. Thus, vaccination releases “proteins called cytokines, which we know from other diseases can disrupt” the menstrual cycle. On the other hand, this side effect remains temporary and benign, underlines the scientist to AFP.