What You Need To Know About Your Menstrual Cycle Post-COVID Vaccine

When COVID vaccines were first administered to the general public in 2021, scientists and medical experts warned of potential side effects. Common post-vaccine symptoms include headache, a sore arm, fatigue, and other temporary symptoms similar to a cold or the flu (per NBC News). As research on the vaccine continues, researchers are noticing another common side effect that can impact people who menstruate.

In a new study published in Science Advances, more than 35,000 people responded to a survey within two weeks of receiving a COVID vaccine. Researchers found that 42% of people with regular menstrual cycles reported changes in their menstruation after the vaccine, including heavier periods or breakthrough bleeding.

Kathryn Clancy, the study author and a professor of anthropology at the University of Illinois Urbana-Champaign, explains to U.S. News and World Report that "the uterus is an immune organ" that can be affected by several immunizations just like other parts of the body.

"People have fatigue and sore arms that are responses to the vaccine, so it's not a stretch to imagine that an immune organ like the uterus, that changes and clots and all these things that are related to the immune system, wouldn't be affected," says Clancy.

Changes in menstrual flow and the uterus have been observed following other vaccines, like the HPV vaccine, but researchers say more work needs to be done in order to determine cause and effect.

Concerns about possible effects on menstruation may have some people hesitant to get vaccinated, but researchers emphasize that the reports only represent a portion of menstruating people, and menstrual changes may vary, if there are any at all (via National Institutes of Health).

"The vaccine doesn't have any long-term consequences, but getting COVID disease will likely disrupt the menstrual cycle much more so," Dr. Taraneh Shirazian, an associate professor and director of the Division of Global and Community Women's Health in the Department of Obstetrics & Gynecology at NYU Langone Health, tells Healthline.

"This information helps us understand that minor cycle changes are possible and common in response to vaccination, so women shouldn't be surprised if their cycles change slightly."

Doctors suggest monitoring your menstrual cycle for any changes following vaccination. In most cases, the menstrual cycle returns to its pre-vaccine regularity quickly (per Medical News Today).

If changes persist, a healthcare provider should be contacted. According to Healthline, signs you may need to see a doctor include if you haven't had a period in 90 days, you have a period more frequently than every 21 days or less often than every 35 days, or if you experience serious pain during menstruation.