Men and women have different reactions to many vaccines, we now know that the COVID-19 vaccine is included on that list.

According to the CDC’s Morbidity and Mortality Weekly Report, 79.1 percent of side effects being reported out of the 6,994 people that reported any side effects at all came from women. The side effects women included were body aches, chills, and flu-like symptoms. 

The reported side effects reported in the were minor by comparison to those from COVID-19. 

A report was done on both of the Covid vaccines (Moderna and Pfizer,) where all 19 of the people who reported having anaphylactic side effects with the Moderna vaccine were female. 44 of the 47 people that reacted similarly to the Pfizer vaccine were women as well.

Women have been known to have worse levels of side effects in past vaccines as well. With the vaccination for the 2009 pandemic flu, women had more severe levels of side effects than men did. 

From an article published in the New York Times, Shelly Kendeffy, a medical technician in State College, PA, reported she and her coworkers all got the second dose of the Moderna vaccine and had very different reactions.

Eight of Kendeffy’s co-workers were male, and seven of them were female. Six women reported feeling very dizzy, had body aches, and chills. Only one man had very mild symptoms and four reported no symptoms at all, but why?

Infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, told Health,

“I don’t think there’s enough information to be able to draw any strong conclusions about why this may be occurring more in females than males.”

Women may be just more likely to report their symptoms more than men, but there is not enough evidence to draw a conclusion for why women appear to have worse side effects.