My Patients Ask — Are women more likely to have COVID vaccine side effects than men?

According to, “Adverse events associated with the Pfizer and Moderna vaccines appear to be more common in women than men.”

CDC analysis of the first 13.8 million doses of Pfizer/Moderna vaccines given in the U.S. showed that 79.1% of side effects reported through VAERS occurred in women, although women made up 61.2% of total vaccine doses given (Gee, MMWR Morb Mortal Wkly Rep 2021).

In addition, the vast majority of cases of anaphylaxis (which were very rare) associated with these vaccines have occurred in women — 94% of anaphylactic cases associated with the Pfizer vaccine and 100% of cases associated with Moderna (Shimabukuro, JAMA 2021).

Although more research is needed, studies of other, non-COVID vaccines have also generally found adverse events to be more common in women, which, experts have suggested may be due to genetic and hormonal differences (such as estrogen’s promotion of antibody production) that can lead to stronger immune responses in women (McCartney, J Obstet Gynecol Neonatal Nurs 2020).

Past research has shown that women tend to produce greater antibody responses (including autoimmune responses) to viral infection and vaccination in general (Scully, Nat Rev Immunol 2020).

However, keep in mind that the CDC also emphasized the inherent limitations of vaccine side effects data collected through VAERS, and noted that anaphylactic rates associated with the Pfizer and Moderna vaccines “are comparable with those reported after receipt of other vaccines.”

This blog was accurate as of the day of posting. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus and the COVID vaccine develops, the information above may have changed since it was last updated. While I aim to keep all of my blogs on COVID and the COVID vaccine up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news.

© Copyright WLL, INC. 2021. This blog provides a wide variety of general health information only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment from your regular physician. If you are concerned about your health, take what you learn from this blog and meet with your personal doctor to discuss your concerns.


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