Could the Covid-19 vaccine have a short-term impact on your menstrual cycle.

Thousands of women think so: ever since the vaccines became widely available, people who menstruate have been sharing stories about weird changes to their cycle following their shots.

This week the BMJ published a report by Dr Victoria Male, a lecturer in reproductive immunology at Imperial College London, noting that a link between the vaccine and menstrual changes was “plausible and should be investigated”.

In the US, the National Institutes of Health recently awarded $1.67m to five research institutions to explore potential links between Covid-19 vaccination and menstrual changes.

There are lots of non-alarming reasons why the vaccine might temporarily affect your cycle.

Dr Male’s report, for example, notes that any link is probably the result of an immune response to the vaccination, rather than anything in the vaccine itself.

Dr Male further notes that most people who report a change to their period after vaccination find it only lasts one cycle.

There is no reason to be worried by a possible link between the Covid-19 vaccine and an abnormal period.

First, there’s the fact that participants in clinical coronavirus vaccine trials weren’t asked specific questions about changes to their menstrual cycle?

Dr Kathryn Edwards, a professor who sits on an independent data monitoring committee for the Pfizer vaccine, told NPR earlier this year that the accelerated speed of development of the vaccines meant that everyone’s energy was focused on spotting dangerous side effects.

“Failing to thoroughly investigate reports of menstrual changes after vaccination is likely to fuel these fears.” Of course it is.

“The menstrual cycle itself is just so incredibly difficult to study, because there are so many other things that may impact it,” one (female) expert told NPR, for example.