Period & COVID-19 Vaccines

Manuela Diaz

Did the Covid Vaccine affect my period? I don’t have a period and it made me bleed?



We have seen the vaccine stickers and heard about the side effects, but now with a 77.8 % vaccination rate amongst Canadians, and with the booster shot being encouraged, menstruators are continuing to report anecdotal changes in their periods. Although not new, hundreds of people have reported changes in their menstruation from delayed periods to heavier bleeding. The Government of Alberta states that the vaccines activate the immune system which can temporarily alter menstruation for a single cycle near the time of the vaccination. The Alberta government further states there is no evidence that COVID-19 vaccines alter menstruation long term. 

Most reports have been anecdotal and some researchers suspect that post-vaccination women are more likely to perceive and attribute period changes to the jab, especially upon hearing and reading about other’s experiences. Although this may be the case some trans folks, people taking hormones to stop their periods and post-menopausal individuals have reported bleeding. This leads reproductive immunologist, Dr. Victoria Male to suspect that there may be a physical reaction to the vaccine. 

“There is an issue about how often women’s health is ignored,” she says.
In a more recent interview with Medical News Today, Dr. Victoria Male mentioned that “the main finding of the study is that people who receive both doses of the vaccine in the same cycle experience, on average, a delay to their next period of 2 days.”

Around half of the population menstruates on a regular basis and many menstruators do not know what to expect with their cycles post-vaccination, which can be quite concerning. Equally as important for trans folks and post-menopausal women bleeding may be an onset of a serious condition such as cancer so it is crucial to know what to expect post-vaccination.


How could vaccines impact menstrual bleeding you may ask? 


There are a variety of theories and hypotheses. One of them being that the menstrual changes are identified by folks experiencing silent ovulatory disturbance. This is where one does not release an egg into their uterus  monthly and is often linked with a fragile endometrium lining and is often displayed as irregular bleeding or spotting. Most folks who experience this are unaware that they don’t ovulate regularly thus may attribute the changes to the vaccine. This however does not explain the changes experienced by trans folks.
The most readily accepted hypothesis is that vaccines may be influencing the hematological and inflammatory systems. A great deal of biological processes rely on inflammatory and immune responses from the body such as the build up and breakdown of the endometrium lining. Post-vaccination the chemical signals and response form the immune cells can affect the endometrium lining. Inflammation has also been seen to affect the timing of ovulation and when derived from infection folks tend to experience more intense premenstrual symptoms. 

In a study conducted by Obstetrics and Gynecology published in Jan 5, 2022, concluded that the COVID-19 vaccination is associated with small changes in cycle length but not menses length. 

Said research tracked nearly 4,000 U.S. women through six menstrual cycles and on average, the next period after a shot started about a day later than usual. But there was no change in the number of days of menstrual bleeding after COVID-19 vaccination.

In an interview with medical today, Dr. Amy Roskin, chief medical officer at The Pill Club — a digital health company — who was not involved in the study said,“the findings were reassuring and reinforced the overall safety of COVID-19 vaccines, as it described a mild and temporary impact on the menstrual cycle length of vaccinated study participants. The authors found that the cycle length change was less than 1 day and temporary, resolving within two post-vaccination cycles.”


What about pregnancy? 

There is no link between the vaccines and miscarriages. Throughout pregnancy different mechanisms maintain and nurture the endometrium lining, most prominently the placenta which links the fetus to the mother and is responsible for nutrient delivery.  

It has been found that other infections are linked with miscarriage and contracting COVID-19 during pregnancy is linked to pre-term delivery by Dr. Alexandra Alvergne at the University of Oxford.

The Government of Alberta echoed this sentiment stating that “there is no evidence that vaccines are harmful when pregnant or breastfeeding. In fact, everyone who is pregnant should get fully vaccinated as they have a higher risk of severe outcomes from variants.”


Why has there been a lack of research? 

This research is indeed difficult to design as periods vary immensely from individual to individual so how do researchers define menstrual irregularities and changes in a large scale study? 

"The menstrual cycle itself is just so incredibly difficult to study, because there are so many other things that may impact it," DR. Laura Riley chair of obstetrics and gynecology at Weill Cornell Medical Center says

Could the lack of research be due to the gender research gap ?

Yes, partly. 

In agreement with female researchers and the history of medical research the gender research gap undeniably contributes to our lack of understanding the effects of the covid vaccine on menstruators. As experts say, the mere fact that vaccine trial participants were not explicitly asked about their periods demonstrates and speaks to the bigger issue about how the medical industry views sexual and reproductive health. Dr Kathryn Edwards, a member of Pfizer’s monitoring vaccine committee, reports that vaccine companies invested funds to monitor the safety of the vaccine and focused on the “truly dangerous” side effects given the gravity of the pandemic. 

Researchers like Dr Katie Lee, a postdoctoral research fellow in the Division of Public Health Sciences at the Washington University School of Medicine in St. Louis attributes some of the gender research gap to the hierarchical distribution of research. The medical field for many years has been dominated predominantly by cisgender men which contributes to the lack of research about women and menstruators in general. 

This is not news. Throughout the history of medicine, we have been collecting data and those who store it have power however most of these figures in the patriarchy as no other than cisgender men. Thus dictating what research is prioritized and sexual and reproductive health does not cut it. 

Bottom line the way we see it


There have been some reassuring results of the short-term effects of the vaccines and we hope these findings will stay true as we navigate life through the pandemic. However we do want to emphasize that although there may be side effects of the vaccine which may include changes in the menstrual cycle similar to the other vaccines these ones appear to only be temporary. We encourage you to get vaccinated and follow local health guidelines! It is also important to educate yourself and others about ongoing research ( and lack-off) of your population in this specific one menstruators and advocate for research on your people!