It's official: the COVID vaccine has an effect on your period

·2-min read
Photo credit: aire images - Getty Images
Photo credit: aire images - Getty Images

A new study has just confirmed what thousands of women and non-binary folk who menstruate have been saying for months: that the Covid-19 vaccine can have an impact on your period. The research has shown that yep, getting the jab can cause changes to your period (such as delaying it, or having a heavier flow), but that luckily, the side effects are short-lived. There's also still no evidence to suggest that getting the vaccine will cause fertility issues.

Now, Dr Victoria Male, an expert in menstruation from Imperial College London, has said that the results are "reassuring", according to the BBC. The US-based study involved close to 4,000 women who use a cycle-tracking app and found that their next period was, on average, delayed by half a day after their second dose, but there was no delay after the first. This comes after more than 36,000 people reporting post-vaccine period irregularities to the MHRA Yellow Card scheme.

It was also found via the study that the cycle length of one in 10 of the women was altered by more than eight days (in contrast with one in 25 unvaccinated women), however their period returned to normal after two cycles.

Photo credit: IsabelPavia - Getty Images
Photo credit: IsabelPavia - Getty Images

American women who received both vaccine doses within the space of one cycle reported a two-day delay to starting their period too, however Dr Male points out that that this likely isn't something that would impact those in the UK, given the longer length of time given between jabs.

Another recent research project from Norway (of over 5,600 people) reinforced how much periods can also vary naturally – due to an array of reasons from diet changes, to stress. Nearly 40% of study participants reported at least one change to their period, even before being vaccinated, the most commonly noted change being heavier than normal bleeding.

The study said that "menstrual disturbances were generally common regardless of vaccination" but that there was a "significant increase in menstrual disturbances after vaccination, particularly for heavier bleeding than usual, longer duration and for short interval between menstruations."

Speaking in more depth about the impact of the vaccine on periods in general, Dr Male said, "Changes to the menstrual cycle do occur following vaccination – but they are small compared with natural variation and quickly reverse. [Concerns around fertility being impacted have arisen] from misinformation that Covid-19 vaccines cause female infertility."

Research from UK-based users of the same menstrual-cycle tracking app is expected to be published soon.

For the latest information on Covid-19, visit the NHS website

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