A few months ago, a friend sent me a link to this viral thread:
(Click the picture to read the thread on Twitter)
Some menstruators have found that their cycles have become more heavy after they received the COVID vaccine.
Others have said they got their period early, or that their periods haven’t stopped.
One person even said that they were menopausal and then got heavy periods after receiving the Moderna vaccine.
Fascinated, I went down a rabbit hole trying to find out more information about this phenomenon.
First, I posed the question to my Facebook friends.
Interestingly, only a few people said they had heavy periods while many explained how they had shifts in their cycle length. One friend said her friend had a period for two weeks after getting the shot, with the second week having significant spotting. Another said that her flow was heavier on the third day, which was not typical. Three said their periods started later, while another said it started earlier. One of my friends said that her first period after her second dose was a week later and shorter, but then the second period was a week earlier and very painful. Yet another said her period was late and more painful than normal as well.
So, based on purely anecdotal testimonies, many of my friends have said that their menstrual cycles changed after getting the vaccine. Of course, there is a confirmation bias in the way I posed my question. There are probably many menstruators who did not have any cycle changes and didn’t comment on my status. Since this is not rooted in the scientific method, no causational linkage can be made, so I tried to find experts in the field who may have answers.
Next, I looked at what the media has said. I received this interview article from a friend, which highlights the expertise of Dr. Heather Huddleston, a reproductive endocrinologist and OBGYN at UCSF. Dr. Huddleston explains that menstrual changes are possibly related to stress instead of the vaccine, but she also says that the immune system plays a role in the uterus. She states that more research needs to be done to understand the link between vaccines and the behavior of the immune system in the uterus.
In another article from the BBC, Dr. Victoria Male, a reproductive immunologist at the Imperial College London, explains that “after vaccination, lots of chemical signals which have the potential to affect immune cells are circulating round the body. This could cause the womb lining to shed, and lead to spotting or earlier periods.”
This led me to dive a little deeper on the connection between the uterus and the immune system. According to Agostinis, et al., the immune system plays an important role in reproduction, specifically regarding paternal/fetal interactions such as trophoblast (cells that form the outer layer of a four day old embryo) invasion and antigen recognition. The endometrium has a noticeable amount of immune cells such as Natural Killer Cells. During the menstrual cycle, the amount and phenotypes of these immune cells change. Unfortunately, I could not find any studies that show if an infection or vaccination can trigger menstrual cycle changes.
A few months after Dr. Kate Clancy’s tweet, she announced that her survey to explore if COVID vaccinations affect periods was approved! All you have to do is complete an online survey which takes 15 minutes or so.
Here is more information about it and how you can do the survey!
Responsible Principal Investigator: Dr. Kathryn Clancy, Department of Anthropology, University of Illinois at Urbana-Champaign (email: kclancy@illinois.edu)
Purpose of the study: This research study is about your experiences with your period or other menstrual bleeding (such as "spotting") and associated symptoms after receiving at least one dose of a vaccine for COVID-19. Side effects are a common and even important element of the vaccine response, and bleeding patterns can be an important way to understand how our immune systems are activated.
Unfortunately, we cannot say for sure if COVID-19 vaccines directly cause changes in the menstrual cycle. Perhaps the changes that menstruators are experiencing is due to the (good) stress of getting the vaccine but not necessarily the components of the vaccine itself. We don’t know. But what I do know is that no matter the menstrual changes, it is our duty to get the vaccine if we can and if it is available to us! Do your part to protect yourself and others!
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