A number of reports about menstrual cycles being temporarily affected after receiving the COVID-19 vaccine are plausible and should be investigated further, according to a medical expert.
More research into the effect of the vaccine on periods remains critical to the success of the vaccination process, London reproduction specialist Dr Victoria Male wrote in her opinion piece for the British Medical Journal on Thursday.
While changes to periods or unexpected vaginal bleeding are not listed as common side effects of COVID-19 vaccination, more than 30,000 such reports had been made to the UK Medicines and Healthcare Products Regulatory Agency (MHRA) surveillance scheme for adverse drug reactions at the start of September.
Anecdotal reports on social media also speak to heavier than usual periods, delayed periods and unexpected bleeding, including this Tweet from medical anthropologist Dr Kate Clancy, who said she experienced an unusually heavy period after receiving the Moderna vaccine.
According to the British Medical Journal, most people find that their period returns to normal the following cycle and, importantly, there is no evidence that vaccination adversely affects fertility.
Period changes have also been reported by some women after infection with the virus itself, and with long-Covid, according to the BBC.
In her opinion piece, Dr Male said "robust research" into reports of period problems would help to counter misinformation around the vaccines, especially when it comes to fertility.
"Vaccine hesitancy among young women is largely driven by false claims that vaccines could harm their chances of future pregnancy," she wrote. "Failing to thoroughly investigate reports of menstrual changes after vaccination is likely to fuel these fears.
"If a link between vaccination and menstrual changes is confirmed, this information will allow people to plan for potentially altered cycles," she said.
Dr Male added "clear and trusted information" was especially important for women who rely on being able to predict their cycles "to either achieve or avoid pregnancy".
"One important lesson is that the effects of medical interventions on menstruation should not be an afterthought in future research," she concluded.