RNA vaccines against Covid have caused menstrual disorders

Since the start of anti-Covid vaccination campaigns, almost two and a half years ago, many women have reported disruptions in their menstrual cycles. Based on these statements, the European Medicines Agency (EMA) ended up including the presence of heavy menstrual bleeding as a possible side effect of messenger RNA vaccines, those from Pfizer/BioNTech and Moderna. But this link remained heavily debated in the scientific community.

A study published this Wednesday, January 24 by the French health authorities provides arguments in favor of the existence of such a link. According to the researchers' conclusions, there is indeed a risk of menstrual disorders from the first injection of a messenger RNA vaccine.

More precisely, the study in question “shows a 20% increase in the risk of heavy menstrual bleeding requiring hospital treatment within 1 to 3 months”, after receiving a Pfizer vaccine or Moderna for the first time, summarizes the Epi-Phare organization, which brings together the medicines authority and Social Security, in particular responsible for protecting individuals in terms of health.

To reach this conclusion, the researchers identified the vaccination status of several thousand women hospitalized for heavy menstrual bleeding in 2021 and 2022. They compared their situation to a control group of women who had not been treated for this reason. . According to the results, the risk of such a disruption of menstrual cycles would be slightly higher the first time a woman receives a Moderna or Pfizer vaccine, each administered in two successive doses. However, it would only be transient, the researchers believe, because it would disappear after three months, even when a booster dose is administered later.

Also readCovid-19: are menstrual problems after vaccination “temporary” and “benign”?

However, not all studies point in the same direction. The present results contrast with those of a large-scale study carried out in Sweden and published in spring 2023 in the BMJ. This had estimated that there was no solid evidence of a link between Covid vaccination and menstrual disorders. According to Epi-Phare researchers, this could be explained by the use of different methodological approaches.

They note in particular that the Swedish study took into account a risk period which began barely more than a week after the patients' vaccination. Such a choice “could have led to masking a possible increase in risk occurring a little later,” explains epidemiologist Rosemary Dray-Spira, who supervised the French study. Conversely, with his team, they chose to wait a month after the first dose of vaccine. Thus, further evidence is needed to consolidate this link.