Women are having most of the reactions to the coronavirus vaccines because they have stronger immune systems!

I wound up on NewsNation, WGN’s TV news show, last night and was asked about the New York Times article that discussed women having more adverse reactions to the RNA coronavirus vaccines. While I think the New York Times’ article is accurate and covers the topic well, there were a few additional points I believe needed to be made to improve our understanding of this phenomenon.

Not all adverse reactions are the same or caused in the same way. The acute allergic reactions that have been reported occur for very different reasons than the inflammatory reactions that follow the second dose of the vaccine. While both may be accentuated in women, they do so for different reasons. 

Allergic reactions have been accentuated in women predominantly for what is thought to be hormonal reasons. Estrogen, the primary female hormone, causes vasodilatation (dilation of the blood vessels). This has been associated with more severe allergic reactions in a number of cases, including peanut allergy. The hormonal effects can potentiate the blood vessel dilatation caused by the allergy.

Women also have a better protective immune system than men. This is based on genetics as many of the genes that control immunity are present on the X chromosome. Because women get two copies of these genes and men only one, men tend to have lesser inflammatory and protective responses. 

Human Chromosomes. Males and females differ as females have two X chromosomes and males only have one, with a second abbreviated copy called “Y.” The Y chromosome lacks most of the genes important to immunity, therefore women have a more robust immune system!

Since women’s immune systems respond more strongly, they have more significant adverse responses to a second dose of vaccine where you’re trying to “boost” preexisting immunity.  These reactions after the second dose of vaccine are a positive sign of protective immunity induced by the vaccine. However, they should be short lived, and if they persist more than 48 hours or worsen over time, you should see your doctor.

Vaccine doses are developed as an average for all male and female subjects. Since women tend to be smaller and often have smaller shoulder muscles (deltoid) where the vaccine is injected, the dose may be proportionally greater for them. This most often results in more severe side effects in women as compared to men, where it may be more likely to lead to inadequate protection. 

A final thought is that in the future, studies may identify different vaccine doses for men and women. This could optimize protection in men, while minimizing side effects in women.

Published by jbakerjrblog

Immunologist, former Army MD, former head of allergy and clinical immunology at University of Michigan, vaccine developer and opinionated guy.

One thought on “Women are having most of the reactions to the coronavirus vaccines because they have stronger immune systems!

  1. “This most often results in more severe side effects in women as compared to men, where it may be more likely to lead to inadequate protection.”

    Articles like these are very disheartening for me. I worked for 25 years in public health, and over that entire time men’s health was at best an afterthought and more often than not thrown under the bus for “more worthy” causes, as the ‘powers that be’ used to tell me when I raised the issue of men’s health.

    The ultimate “side effect” of COVID-19 is death, and when one looks at all of the peer-reviewed science that’s been done throughout the world since the beginning of the pandemic that I’ve been able to find, when death rates are stratified by sex those studies show that anywhere from 60 to 75 percent of deaths that occur once someone contracts COVID-19 are men. So let’s cut that down the middle and say that ~66% of deaths are men; that makes a 2:1 ratio of men vs. women who actually die from the virus. I think that a two-to-one death ratio is a pretty big deal, however, the public health community seems to ignore this when developng policy re. vaccine priorities, etc.

    One can speculate ‘til the cows come home re. the reasons that this aspect of the pandemic is ignored, but one cannot speculate about the science and facts – they are what they are: men are basically twice as likely to die from COVID-19 than are women once we get it. Can we all please just at least acknowledge this and perhaps talk about it? And maybe even take that into consideration vis-a-vis the decision-making processes with respect to dealing with the pandemic?

    Liked by 1 person

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