When COVID-19 vaccines first became available, some people noticed unexpected menstrual bleeding after receiving their shots. Some trans men were among those affected, which must be very weird if you thought you were done with your period and all of a sudden you start having your period.
Menstrual changes or unexpected bleeding were not tracked in the original studies of COVID vaccines, so no one has been able to tell if these changes were part of a vaccine-related pattern. So a team of researchers circulated a survey asking people about their menstruation-related experiences with the vaccine, and now the results have been published. In short: IIf this has happened to you, you are definitely not alone.
How many people had heavier or unexpected bleeding after their vaccine?
Before telling you the results, there is One thing that’s important to know: the survey is not based on a representative sample, so we don’t know how common these menstrual side effects were in the general population. We just know how common they were among people who responded to the survey. On the one hand, people who had problems were perhaps more likely to respond to the survey; but the researchers note that there may be reasons why people who have had changes in their bleeding or new bleeding might be less likely to respond to the survey. At the end of the day, we do not know.
With that, here are the results:
Among respondents with normal menstrual cycles, 44% said their cycle continued normally and 42% said they had heavier bleeding. Among people who don’t usually menstruate but used to, the majority of respondents reported breakthrough bleeding. This included 71% of people on long-acting reversible contraceptives such as IUDs, 66% of people past menopause, and 39% of people on gender-affirming hormones.
Why did this happen?
We don’t know why this happened, but the study authors say it was premature to tell women last year that there was ‘no biological mechanism’ by which a vaccine could cause breakthrough menstrual bleeding.
But the authors note that changes in menstruation have been reported with other vaccines in the past, including typhoid, hepatitis B and HPV vaccines. And since the uterus has to switch between bleeding, clotting, and repairing functions, which involve the immune system, something like a vaccine that activates the immune system and causes inflammation can presumably affect those processes. Lead Writer Kathryn Clancy told tech networks“When the immune system is activated by something like a vaccine, it’s going to have all kinds of downstream effects, including on the uterus.”
This does not mean Bleeding is necessarily bad for your health. The authors note that “the uterine reproductive system is flexible and adaptable in the face of stressors to overcome short-term challenges in a way that leaves long-term fertility intact.” We already know that stress (both physical and psychological) can have effects on the menstrual cycle.
That said, if you are bleeding you do not expect it, it may be a good idea to have yourself examined. Unexpected bleeding when you do not have your period normally can sometimes be an early sign of cancer. But it is useful to know that it can too be a side effect of a COVID vaccine.
At the end of the day, we still don’t know why the heaviest bleeding and breakthroughs happened, and we don’t know how common they were. But at least there is information to tell yes, that’s one thingand researchers are studying it further.