People have reported menstrual cycle changes after COVID-19 vaccines, but more research is needed to understand if they are related, which women may be affected, and the exact mechanisms for why.

People have reported menstrual cycle changes after COVID-19 vaccines, but more research is needed to understand if they are related, which women may be affected, and the exact mechanisms for why.

Update: October 5, 2021

NICHD recently awarded five institutions one-year supplemental grants totaling $1.67 million to explore potential links between COVID-19 vaccination and menstrual changes. Researchers at Boston University, Harvard Medical School, Johns Hopkins University, Michigan State University, and Oregon Health and Science University will investigate whether such changes may be linked to the COVID-19 vaccine itself or if they are coincidental, the mechanism underlying any vaccine-related changes, and how long any changes last.

Several of these studies will use blood, tissue, and saliva samples collected before and after vaccination to analyze any immune or hormone changes. Other studies will use established resources — such as large cohort studies and menstrual cycle tracking apps — to collect and analyze data from racially, ethnically, and geographically diverse populations. Two studies will focus on specific populations, including adolescents and people with endometriosis.

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.

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 and how vaccination as well as other factors, such as stress, might influence menstrual changes.

Why is this research important?

As more people are vaccinated for COVID-19, it is possible to gain better understanding of short- and long-term effects of the vaccines. Scientific evidence could also help unvaccinated people understand what, if any, menstruation-related side effects to expect from a 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 possible effects of the COVID-19 vaccine on menstruation.

Menstruation and Menstrual Problems

  • NICHD shares information about menstruation and menstrual cycle irregularities.

Sources

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. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7522626/

This article has been updated and edited for clarity.

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Page last updated: October 5, 2021