COVID-19 Vaccines Do Seem To Impact Periods—Researchers Are On The Case

by Wendy Wisner
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First, before I get into the details of this article, I want to emphasize that experts agree that vaccines causing changes to our menstrual cycles is not a cause for alarm, nor is it a reason not to get vaccinated against COVID-19. There is no evidence that the COVID vaccines cause lasting changes to menstruation, and there is no evidence that the vaccines cause fertility issues.

COVID-19 vaccines are considered safe, effective, and are our the primary way we are going to end this pandemic. Like other common reactions, including sore arms, fevers, and fatigue, vaccines can have temporary effects on your entire body. That’s to be expected, and temporary changes to the menstrual cycle are one possible change.

Got it?

Cool, now that we’ve gotten all that out of the day, I’m going to tell you a little story. Since I first started having periods, I’ve had the most regular menstrual cycles in the world. I get my period once per month, I rarely spot in between, I have classic ovulation signs each month, and I bleed normally for 3-5 days. Besides pregnancy and the first few months of breastfeeding, I’ve never missed my period, or had a super early or late period.

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That’s why I was totally surprised what happened the month that I got my COVID-19 vaccine. I got my first shot around the time that I would normally ovulate. My initial side effects from the vaccine were just a very sore arm and fatigue. But I also noticed that I wasn’t experiencing many of my classic ovulation signs, even though I usually experienced them like clockwork.

About a week later, I seemed to have ovulated, though, so I figured that things were on track. But then, just a few days after that, I started spotting. “WTF,” I thought, assuming I got my period early. I experienced some kind of weird, light period for an entire week, and thought that was it. It wasn’t, though. Soon after the weird, light period was over, I started getting menstrual cramps, more intense ones than usual.

And then—I kid you not—I had the heaviest period I’d had since I was a teenager. I had to wear those bulky, overnight pads for five days straight, and I kept thinking I was going to soak through on everything I sat on. It was bonkers. Thankfully, besides the heavy flow, I was fine, and then it was all over.

Extremely curious, I took to Dr. Google to figure out what the heck was happening. It turned out I was far from alone. I found a Twitter thread by Dr. Kate Clancy, who’d experienced a similarly heavy period post-vaccination. She was taking an informal poll to see if others had experienced weird periods, and HOLY CRAP, they most certainly had.

There were people like me who’d experienced “the heaviest period since they were 13.” There were folks who hadn’t had a period in years and then got one out of the blue after their shot. People who were in menopause who started bleeding again. Etc.

It wasn’t just this Twitter thread either. There were reports all over social media of folks who shared very similar experiences. I posted about it on my personal Facebook and many of my friends had experienced the same thing.

Now, it should be emphasized that all this info is anecdotal, and that no one knows why this was happening and even if there was a clear enough relationship between the vaccine and these menstrual changes. It seems like there had to be, right? But none of us are scientists. Plus correlation doesn’t equal causation—i.e., just because one thing happens at the same time another thing happens, doesn’t necessarily mean the two are related.

It also should be noted that in most (if not all) of the instances reported, nothing else troubling happened. Most had one or two weird periods, and things were back to normal. My experience was that I had that one weird period, and haven’t had any weird periods since.

Thankfully, doctors and scientists did listen to all this chatter on social media, and are now doing to look into this issue.

As Business Insider notes, after 30,000 women in the U.K. reported disruptions to their menstrual cycle after their COVID vaccine, researchers are urging an investigation into why this is happening and if there are any concerns. Dr. Victoria Male published a paper in the British Medical Journal explaining why an inquiry into these claims are important.

Dr. Male explains that changes to the menstrual cycle after the COVID shot are “short lived,” but that “robust research into this possible adverse reaction remains critical to the overall success of the vaccination programme.”

She believes that understanding why the vaccines are affecting our cycles the way they have will decrease vaccine hesitancy among people who find the rumors circulating about menstrual effects troubling.

“Vaccine hesitancy among young women is largely driven by false claims that COVID-19 vaccines could harm their chances of future pregnancy,” Dr. Male writes. “Failing to thoroughly investigate reports of menstrual changes after vaccination is likely to fuel these fears.”

I totally agree with her. Knowledge is power. Women know that the vaccines are affecting their cycle. If they understood—as most doctors speculate—that these changes are innocuous, and don’t have long-term effects, they would trust the vaccines even more.


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Researchers in the U.S. are taking things a step further and actually beginning a study into this matter. The National Institutes Of Health is granting $1.67 million dollars to five different institutions and asking them to look into the relationships between COVID-19 shots and changes in menstruation.

Like Dr. Male, The National Institutes Of Health hopes that research into this issue will ease fears about the vaccine and its effects on women’s bodies.

“These rigorous scientific studies will improve our understanding of the potential effects of COVID-19 vaccines on menstruation, giving people who menstruate more information about what to expect after vaccination and potentially reducing vaccine hesitancy,” NICHD Director Diana W. Bianchi, M.D., said in a press release.

The National Institutes Of Health’s press release also offered some hypotheses about what is causing all these menstrual changes. They point that lots of things may have affected women’s menstrual cycles at the time these changes were reported, including pandemic stress, changes in lifestyle as a result of the pandemic, and even infection with COVID-19.

As for how the vaccine specifically may have affected women’s menstrual cycles, the National Institutes Of Health explains that menstrual cycles are “regulated by complex interactions between the body’s tissues, cells and hormones,” and that the immune response to the vaccine “could affect the interplay between immune cells and signals in the uterus, leading to temporary changes in the menstrual cycle.”

Pretty freaking fascinating, huh?

I totally agree that we need more information about this topic, and it’s kind of crazy that menstrual side effects weren’t investigated when the vaccines were first being developed (because, hello, women’s bodies are super sensitive to this kind of stuff, and this is important information for us to know).

Still, I think it’s great news that this issue is going to be investigated further. While it’s great that so many of us are sharing our post-vaccine period stories, without good data, these sorts of things can lead to tons of misinformation and unnecessary fear.

Again, despite not fully being studied yet, experts agree that the vaccines are safe for menstruating people, the menstrual effects are temporary and not harmful, and they won’t affect your fertility. Stay tuned for more research on this topic, but rest assured that you can safely get your vaccine, if you haven’t already.