Menstrual Irregularities and the COVID-19 Vaccine?

nurse in mask giving woman an immunizationReports have begun to appear in mainstream and social media about an association between the COVID-19 vaccine and menstrual irregularities. This is very disappointing—not because the question shouldn’t be studied; but rather, because the reports thus far offer no scientific evidence whatsoever. Unfortunately, they do grab attention—exactly their purpose. For example, NPR covered the topic this week in its popular morning segment All Things Considered.

The headline read: “A Possible Side Effect? Thousands Of People Saw Menstruation Changes Post-Vaccine.” What was this about? The NPR commentator reviewed the post-vaccine experiences of two women, Dr. Katharine Lee and her friend Dr. Kate Clancy. These women are not MDs or PhDs in any of the medical sciences. They are anthropologists.

Dr. Lee commented, “I’m on the Mirena IUD, so I normally don’t experience a period. And so I had breakthrough bleeding and cramping, which for me is really, really unusual. “She shared this with her friend Dr. Clancy who affirmed that she had experienced a heavier-than-normal menstrual period after her shots. The two women—from among 165 million fully vaccinated people in the U.S., more than half of them women—decided to investigate whether their personal experience could be a vaccine side effect. Instead of the classic methods relied upon to produce high-quality research since the 17th century, the two young scientists chose a newer tool. Clancy and Lee posted a survey to Twitter. From Dr. Clancy, “We started hearing a lot about breakthrough bleeding from people on long-acting, reversible contraception… and postmenopausal people who were years and years out from their last period, sometimes decades out.”

Of course, this is not scientific evidence. Social media are, by their nature, a place for people to tell their personal stories with no filter or control for accuracy. Twitter is entertainment. But social media can have a powerful and harmful influence on women’s personal health decisions if trusted news and information sources present this chatter as “science.”

If this story or others like it caused you concern about your own vaccine status, keep in mind:

  • The FDA has not currently seen evidence that the vaccines cause menstrual irregularities.
  • A common side effect of long-acting birth control methods is break-through spotting or bleeding—whether or not you have been vaccinated. It is annoying but harmless.
  • Nearly 10% of ALL women—vaccinated or unvaccinated–experience an episode of spotting or bleeding after menopause. We always investigate this symptom because a small number of these cases may turn out to be cancer.
  • If, coincidentally, a woman has an episode of irregular bleeding near the time of her vaccination, she may believe the two are related.
  • Government and independent researchers will continue to investigate reports of vaccine side effects using reliable scientific methods. But, with 348 million doses already given in the U.S., we are confident that any truly harmful vaccine side effect would already have been exposed.
  • If more data begins to tell us that women are experiencing any of these very common menstrual irregularities more frequently than non-vaccinated women, recommendations about the importance of COVID-19 vaccination are not likely to change. Mild discomfort or inconvenience does not compare with the potential for a tragic outcome from COVID illness.

I recommend vaccination to my patients because high-quality scientific study has shown they are safe even during pregnancy and pose no future reproductive risk. In my medical judgement, the benefits outweigh any possible risk. If what you hear or read causes you concern, ask your own doctor.

With best wishes for your family’s health.

Judi Favor MD