At least 32 people (out of around 56,000) have reported these changes so it may not be a very common side effect – but doctors agree it’s something we need to look at.
The research around this is quite limited right now and most stories are purely anecdotal at this stage – but a formal study has just been launched by Dr Kate Clancy and Dr Katherine Lee.
Katherine, a post-doctoral scholar in the public health sciences, got her vaccine early on in the pandemic on the same day as a friend, so afterwards they compared side effects.
They both noticed that their period had come earlier than usual, and Katherine spoke to other friends and family members as they got vaccinated, with a few more noting changes to their periods.
She then reached out to Kate an associate professor at the University of Illinois studying harassment, discrimination, stress, and menstrual cycles.
Shortly after the pair connected, Kate got her vaccine and she too noticed she had an unusual period, so she posted about it to her Twitter followers.
A colleague told me she has heard from others that their periods were heavy post-vax. I'm curious whether other menstruators have noticed changes too? I'm a week and a half out from dose 1 of Moderna, got my period maybe a day or so early, and am gushing like I'm in my 20s again.
— Dr. Kate Clancy ????️???? (@KateClancy) February 24, 2021
Since then, other people have shared their own experiences, with some saying they were having a period for the first time in years, and others saying their first period after the vaccine was so heavy, they had to call emergency service.
After seeing the response, Kate began to discuss what could be happening.
“Does this have to do with the way the vax response is mounting a broader inflammatory response, possibly moreso because of the lipid nanoparticle or mRNA mechanism? Either way I am fascinated! Inflammation + tissue remodeling = extra bleedypants!’
From there, Katherine and Kate launched a formal study to collect experiences of having a period after getting vaccinated.
In the US, the Centers for Disease Control and Prevention (CDC), has been checking side effects through the Vaccine Adverse Event Reporting System (VAERS).
At least 32 people (out of around 56,000) have reported changes to their periods so it may not be a very common side effect – but doctors agree it’s something we need to look at.
Dr Elise Dallas, at GP at Babylon, says:
“There is currently research going on about if the vaccine impact on periods making them heavier, slightly irregular and possibly more painful if you already have underlying endometriosis or adenomyosis.
“This is not proven and currently anecdotal evidence at the moment.
“The mechanism is unclear but we have always known that stress, poor sleep, exercise, and some medications, can impact the menstrual cycle. We know that oestrogen is beneficial in Covid and immunity and this could have an affect on the menstrual cycle.”
Dr Ashfaq Khan, consultant obstetrician & gynaecologist, Harley Street Gynaecology, adds that it’s important to stress there is no evidence that the vaccine impacts fertility – but it could have a short term impact on menstruation.
He tells Metro.co.uk:
“Some women have reported that their first period after having received a Covid vaccine is a little irregular with regards to either timing or flow. While there is absolutely no evidence that any of the vaccines impact on fertility, menstruation sensitivity could be an as yet unresearched side effect.”
There is also some evidence that having Covid can impact your menstrual cycle.
Ashfaq points to a study, which found that around 20 to 25% of the 177 women of childbearing age who provided menstrual data were affected in this way. Although none of the vaccines contain the virus, it could be related to the antibodies produced.
He further adds:
“Although research is still ongoing, we do know that Covid can impact menstruation and although the vaccinations do not contain the Covid virus, it may be that the antibodies produced by the body in response to the vaccination are what triggers the changes in the period. Other theories currently being considered are variations in estrogen levels and inflammation.
“Whatever the cause, doctors are quick to reassure women that any subsequent changes to menstruation are temporary and are not dangerous. If a woman continues to experience significant differences after the first cycle, she is advised to contact her health professional.”