‘There’s good biological plausibility’ that vaccines affect menstrual cycles, OB-GYN says

May 06, 2021
Woman's hand reaching into pink purse to get sanitary supplies.
Some women report needing more sanitary supplies than usual after getting vaccinated. Photo illustration by Sarah Pack

If you check out a website called VAERS, the Vaccine Adverse Event Reporting System, you’ll find comments from and about women who say they had period problems after getting a COVID shot. These are anecdotal reports, and anyone can submit one.

But obstetrician and gynecologist Jessica Tarleton at MUSC Health said there may be something to them. “We don’t really know. But we do know that if people get sick, or undergo stress, it can affect your menstrual cycle. If you have weight gain or weight loss, that could also affect your menstrual cycle. So it wouldn't be the craziest thing for a vaccine to temporarily affect an individual's menstrual cycle.”

“Menstruation started within 24 hours” of vaccine “and two weeks early in cycle,” one VAERS report says.

“I had severe menstrual bleeding, soaking thru tampon every 30 minutes,” reads another.  

“Started menstrual cycle 36 hours after the vaccine. Had not had it for two years.”

“Missed cycle. Has had normal cycles for past eight years.”

Tarleton, a reproductive health specialist who has both a medical degree and a master of public health degree, has had a few of her patients say their periods were off after getting vaccinated. She wasn’t surprised.

“The vaccine is designed to affect our immune system, and our immune system affects our menstrual periods. I think there’s good biological plausibility that that could be happening, meaning there are biological explanations to explain some connection between vaccines and menstrual periods, although it has not been studied.”

If it happening, is it harmful? “If a vaccine is causing an irregular period, I would argue that there is not a problem with that,” Tarleton said. “Any effect on bleeding and days of a period, or even painful periods, is — if anything — temporary, and unlikely to significantly affect someone's health.”

Meanwhile, Tarleton, an associate professor in the College of Medicine at the Medical University of South Carolina, says there’s no evidence the vaccines cause fertility problems, pregnancy issues or trouble for women who are breastfeeding. And the Centers for Disease Control and Prevention says pregnant people are actually at an increased risk of getting severely ill if they get COVID-19.

But Tarleton does want to clear up a misconception that’s been in the news lately. Vaccinated people cannot “shed” the COVID vaccine onto other people and make them sick or cause reproductive problems.

“I don't think it’s possible to emit something from your body that could attach to someone else. This is a not a live-virus vaccine,” Tarleton said. “Some of our vaccines are live-virus vaccines, like measles, mumps and rubella, for example, or chickenpox. It’s theoretically possible that if you have a live virus in your body it could possibly be transmitted to someone else, but for a vaccine that is not live, it's kind of impossible.”

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