FEB 02, 2022 11:00 AM PST

What you need to know about the COVID-19 vaccine and menstrual cycle

WRITTEN BY: J. Bryce Ortiz

Does the COVID-19 vaccine affect menstrual cycle regularity? This question has been popular in the mediaand on social networks since the vaccines were first available to the general public in the beginning of 2021. However, research into the topic was sparse at the time. Since then, several scientific studies have provided data that shows that the COVID-19 vaccine may lead to small, and short-lived changes to the normal menstrual cycle. 

The findings from two recent studies are discussed in an exceptional editorial article published last week in the British Medical Journal. The article was authored by Dr. Victoria Male, a lecturer in reproductive immunology at Imperial College London. In short, Dr. Male said, “changes to the menstrual cycle do occur following vaccination – but they are small compared with natural variation and quickly reverse.”

In one of the recent studies, researchers obtained data from close to 4,000 individuals who used a menstrual cycle tracking app on their phone. The researchers were able to track menstrual cycle regularity by comparing menstrual cycles from before vaccination to menstrual cycles after vaccination, in the same individuals. They then compared the pre- and post-vaccination cycles to the menstrual cycles of individuals who did not receive the vaccine. 

They found that, in normally cycling individuals who received the vaccine, an increase in menstrual cycle length of less than 1 day was observed. Although, as Dr. Natalie Crawford says in the video below, the change in menstrual cycle of less than one day in length is not clinically significant, meaning this would have no genuine or noticeable effect on daily life. 

While the cause of vaccine-induced cycle changes is unknown, Dr. Alison Edelman, the lead researcher on the study says that the data are reassuring and validating for the thousands of women who have reported changes to their menstrual cycle following COVID-19 vaccination. As menstrual cycles, and women’s health issues in general, are largely ignored or underdiagnosed by the healthcare community. 

“The menstrual cycle is like the stepsister that gets ignored. It’s considered unimportant in the grand scheme of things,” said Dr. Edelman, “but it actually really is important to people day-to-day.” Additionally, Dr. Diana Bianchi, director of the National Institute of Child Health and Development, said, “It is reassuring that the study found only a small, temporary menstrual change [… and] these results provide, for the first time, an opportunity to counsel women about what to expect from COVID-19 vaccination so they can plan accordingly.”

As more studies begin to emerge on the effects of the COVID-19 vaccine, healthcare professionals continue to urge all eligible individuals to receive the COVID-19 vaccine and booster shots. The COVID-19 vaccine has been shown to be safe, effective, and live-saving for women, including pregnant women and women who are trying to become pregnant. 


Sources: SF ChronicleTwitterObstetrics & GynecologyPreprint SSRNThe British Medical JournalJournal of Women's HealthBBCVox

About the Author
Doctorate (PhD)
Science and medical writer | Researcher | Interested in the intersection between translational science, drug development, and policy
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