vaccine and periods

As the COVID vaccine rollout continues apace, by now we all know someone who’s had a reaction to the jab.

The potential side effects are all well documented, and unlikely to cause any long-term damage. When you attend your vaccination, you will be given a list of possible symptoms you might experience over the next few days. These include:

  • fever
  • headache
  • sore arm
  • aching joints
  • nausea
  • tiredness

One thing you might not expect to experience is a change to your menstrual cycle. In fact, an increasing number of women are reporting unusually heavy or painful periods post vaccination.

Increasing anecdotal evidence

Medical anthropologist Dr Kate Clancy experienced changes to her usual menstruation pattern after having the Moderna jab. She took to Twitter to recount her tale. Within days, dozens of women got in touch to say the same thing had happened to them.

And it’s not just pre-menopausal women who are experiencing bleeding after being vaccinated. Dr Victoria Male, a reproductive immunologist at Imperial College, London, says she has received reports from post-menopausal women. Even people who are taking hormones to prevent bleeding have claimed to have had something akin to a period after receiving their COVID jab.

There has so far not been a study into the effects of the vaccine on periods. But Dr Clancy – together with former colleague Dr Katharine Lee – has launched a survey on the subject. It has the potential to develop into a study at a later date. Again, there have been some surprising responses, including some trans men.

Why would the vaccine affect periods?

While it might seem unlikely at first glance, medical professionals stress that there is a plausible explanation for vaccination to affect your periods, and it’s really nothing to worry about.

Periods are caused when the womb lining, which has built up over the course of your cycle in preparation for harbouring an embryo, breaks down and leaves your system.

This womb lining is actually part of your immune system – designed to protect the foetus from anything that might be happening elsewhere in your body. So immune cells play a part in this process of building up and breaking down.

The whole point of vaccination is to stimulate the immune system, so it is reasonable to suspect that this could cause the usual process to go into overdrive.

Could this lead to miscarriage?

There is no evidence to suggest that this could cause miscarriage in pregnant women. Once the foetus is in situ, a different process is involved in maintaining the womb lining.

In fact, there is now extensive evidence to show that there is no risk of pregnancy loss from having the COVID vaccination. Contracting the virus itself in pregnancy, however, could have some very serious effects, so official advice is now for pregnant women to be vaccinated.

For more information or to discuss any concerns you may have about your own menstrual cycle, please contact us.