A European Medicines Agency (EMA) committee on Friday recommended adding heavy menstrual bleeding as a side effect of mRNA COVID-19 vaccines made by Moderna , as well as partners Pfizer and BioNTech .

Reports of heavy periods - bleeding characterized by increased volume and/or duration that interferes with the quality of life - have been observed during clinical trials, from cases in the real world and in medical literature, the EMA said.

The cases - which have mostly been non-serious and temporary in nature - have been reported after the first, second and booster doses of Pfizer-BioNTech's Comirnaty and Moderna's Spikevax, it added.

The regulator has now concluded that there is at least a "reasonable possibility" that heavy menstrual bleeding is causally associated with these vaccines.

Menstrual disorders can occur due to a range of reasons, including underlying medical conditions as well as stress and tiredness. Health authorities have highlighted that cases have also been reported following COVID-19 infection.