COVID-19 vaccination linked with small, temporary changes in menstrual cycles

July 26, 2022 – Vaccines for COVID-19 may cause small changes in menstrual cycles, but those changes are temporary, according to preliminary results from the Apple Women’s Health Study.

The study’s survey of over 9,600 participants found that, on average, a dose of vaccine was associated with an increase in menstrual cycle length of about half a day. Cycle length returned to the pre-vaccination average in the following cycle.

“Our preliminary insights … emphasize that menstrual cycle changes associated with COVID-19 vaccination are small and temporary and should not discourage people from getting vaccinated,” according to an update on the Apple Women’s Health Study website.

Research collaborators on the Apple Women’s Health Study include Harvard T.H. Chan School of Public Health, the National Institute of Environmental Health Sciences (NIEHS), and Apple.

Read the update about the study: COVID-19 vaccines and menstrual cycles

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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