Covid-19: Vaccines may cause menstrual problems, study finds

Anti-Covid vaccines causing menstrual irregularities? Yes, according to the results of a study published Wednesday by French health authorities that suggests the risk of menstrual irregularities increases slightly in the three months after receiving the Covid messenger RNA vaccine, although the association remains. is discussed in the scientific community.

The study “shows a 20% increase in the risk of heavy menstrual bleeding requiring hospital treatment for 1-3 months” after first receiving the Pfizer or Moderna vaccine, summarized in a press release from Epi-Phare, which cited the Medicines Agency (ANSM) together. ) and Social Security.

Heavy menstrual bleeding

Since Covid vaccination campaigns began almost two and a half years ago, many women have reported menstrual irregularities. Based on these claims, the European Medicines Agency (EMA) eventually included the presence of heavy menstrual bleeding as a possible side effect of the Pfizer/BioNTech and Moderna messenger RNA vaccines.

However, research on this issue remains controversial, and the Epi-Fare study provides evidence to support the existence of such a link. Researchers determined the vaccination status of several thousand women hospitalized for heavy menstrual bleeding in 2021 and 2022. They compared their situation with a control group of women who were not treated for this reason.

They ultimately concluded that the risk of such menstrual irregularities is slightly higher when a woman first receives the Moderna or Pfizer vaccine, each given in two consecutive doses. The risk persists for three months and then, even after a subsequent booster dose, disappears. These results contrast with those of a large-scale study conducted in Sweden and published in spring 2023 in the BMJ. There was no convincing evidence of a link between Covid vaccination and menstrual irregularities, experts said.

When asked about these different findings, Epi-Phare researchers pointed to differences in methodology. They note in particular that the Swedish study took into account a risk period that began just over a week after patients were vaccinated. Such a choice “could have the effect of masking a possible increase in risk that would occur a little later,” explained epidemiologist Rosemary Dray-Spira, who oversaw the French study, with the latter choosing to wait a month after the first dose of the vaccine.