Vials with Pfizer-BioNTech and Moderna coronavirus disease (COVID-19) vaccine labels are seen in this illustration picture taken March 19, 2021.
The European Medicines Agency's safety committee said on Friday it was reviewing reports of heavy menstrual bleeding and absence of menstruation from women who had received Covid-19 vaccines from Pfizer/BioNTech and Moderna.
The assessment was in view of reports of menstrual disorders after receiving either of the two vaccines, both based on messenger RNA technology, and it was not yet clear whether there was a causal link, the agency said.
Menstrual disorders can occur due to a range of underlying medical conditions as well as from stress and tiredness, the EMA said, adding that cases of such disorders had also been reported following Covid-19 infection.
Vaccination against Covid-19 was linked with a small, temporary change in menstrual cycle length, according to a recent study funded by the National Institutes of Health, which collected data from nearly 4,000 users of a smartphone app that tracks menstrual cycles.