The COVID-19 vaccine may affect menstrual cycles, but more research is needed to understand the exact mechanism and which people are more likely to be impacted.

What you need to know

Increased stress, changes in weight and exercise, and other major lifestyle changes can affect menstrual cycles — and all of those changes are common during the COVID-19 pandemic. Additionally, studies have shown that some women who had COVID-19 experienced changes in the duration and flow of their menstrual cycles.

But menstrual cycle changes may not be limited to those who get COVID-19. Recently, some people have reported changes in their menstruation after receiving the COVID-19 vaccine, including changes in duration, flow, and accompanying symptoms such as pain.

What will researchers be doing?

To learn whether there is a connection between vaccination and changes in menstruation, the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) recently released a notice of special interest for researchers to compare the menstruation experiences of vaccinated and unvaccinated people. NICHD will support research focused on menstruation before and after vaccination, how the vaccine affects menstruation, and the influence of other factors, such as stress, on these menstrual changes.

Why is this research important?

As more people continue to get vaccinated for COVID-19, understanding the short- and long-term effects of the vaccine on reproductive health will be important. Scientific evidence will also help unvaccinated people understand any menstruation-related side effects of the COVID-19 vaccine.

Where can I go to learn more?

Notice of Special Interest (NOSI) to Encourage Administrative Supplement Applications to Investigate COVID-19 Vaccination and Menstruation

  • NICHD calls on researchers to study the effects of the COVID-19 vaccine on menstruation.

Menstruation and Menstrual Problems

  • NICHD shares information about menstruation and menstrual cycle irregularities.


Li, K., Chen, G., Hou, H., Liao, Q., Chen, J., Bai, H., Lee, S., Wang, C., Li, H., Cheng, L., & Ai, J. (2021). Analysis of sex hormones and menstruation in COVID-19 women of child-bearing age. Reproductive Biomedicine Online, 42(1), 260–267.

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Page last updated: August 2, 2021