vaccines on a blue background representing women having vaccines

Why Are Women Having a Higher Immune Response to COVID-19 Vaccines?

By now, most of us know about the side effects from the COVID-19 vaccines—headaches, chills, nausea, fatigue, and soreness at the injection site. (And, for the Johnson & Johnson vaccine, in rare cases it has been linked to blood clots.) But did you know 79% of the people experiencing these side effects are women? 

Researchers say the side effects can indicate greater immunity. This means women are showing a greater immune response to COVID-19 vaccines than men.

What makes females have a stronger immune response than males?

There are multiple theories on why female immune systems seem to react stronger than males. Most theories focus on biological, cultural, lifestyle, and social factors. 

(Note: in this post the words “male” and “female” are used in reference to an individual’s sex assigned at birth.)

Biologically, women can have a predisposition for immunity due to large amounts of “T helper cells” which, according to Dr. Daniel Saban, immunologist at Duke University, activate other cells in our immune system to make antibodies and fight a virus. Also, several types of immune cells have estrogen receptors on them, and with women producing much higher amounts of estrogen than men, it gives them a higher chance for immune response. 

Longevity can also be a factor, as women live longer than men. This would explain why more men are becoming infected and dying from COVID-19 than women in every age group until the 85+ years group. (Women are the majority in that age group.)

Culturally, there’s a strong component influencing immune response—exposure. Women still hold the majority of roles that work and care for children and the elderly. This exposure to the most vulnerable populations could give women a higher chance of developing antibodies for various diseases and infections than men.

(For the COVID-19 vaccines specifically, women make up over 50% of the workforce in healthcare and education, two of the largest fields on the frontlines who are prioritized to get the vaccine.)

Lifestyle is another important consideration as most heavy drinkers and smokers are male. The short-term and long-term side effects of alcohol and tobacco are linked to lowered immunity making it harder to fight off disease and infections.

Finally, due to social reasons, men may be less likely than women to seek out the COVID-19 vaccine, other vaccines, or healthcare in general. And the men that do get the vaccine are less likely to report side effects and symptoms. While it’s a generalization, the societal pressure that discourages males from seeking help or reporting problems still exists— especially in healthcare.

The COVID-19 vaccine isn’t the only vaccine women respond better to

A 2018 study of the flu vaccine found that it was 49% effective in females and only 38% effective in males. The study also showed that women had more side effects AND a stronger immune response to the vaccine than men. 

Researchers noted that women’s greater immune response could be related to their greater propensity for seeking healthcare and naturally higher immune response.

“Women and girls produce sometimes twice as many infection-fighting antibodies from vaccines,” Rosemary Morgan, a research scientist at Johns Hopkins Bloomberg School of Public Health, told USA Today

 So, do women respond better to all vaccines than men?

Honestly, we don’t know. Why do women live longer than men? Why are more men diagnosed with cancer than women? Scientists aren’t quite sure—yet. We need more research on how male and female immune systems operate and respond to diseases and vaccines. 

Research on the COVID-19 vaccines is ongoing, and there isn’t enough data yet to say why they’re affecting females vs. males differently. Also, we don’t have enough long-term data on how vaccines in general affect females vs. males due to gender bias in clinical trials. 

Gender bias in clinical trials is a sore spot for the medical research community. Only recently have efforts have been made to rectify this. There wasn’t an official rule for women to be included in clinical trials until the 1993 National Institutes of Health Revitalization Act passed to make sure women and other minorities were included in clinical research. 

With less than 30 years of gender equality in medical research, we have a large gap in medical knowledge and information on how well females vs. males respond to vaccines, drugs and medications. 

We know it is a crucial mistake to not differentiate males and females in clinical trials as it affects outcomes. In a 2016 study on women’s roles (or lack thereof) in clinical trials, researchers noted:

“These deficiencies have hindered the progress of understanding women’s response to medications… agencies in the United States have worked towards the inclusion of women in clinical trials and appropriate analysis of sex-specific data from clinical trials.”

We know some of the factors that affect and influence female vs. male immunity, but we don’t know everything. How females and males as individual sexes respond to drugs, vaccines and diseases matters—it’s an essential part of understanding their health and wellbeing.

How can medical professionals accurately assess, diagnose, and treat each patient if they don’t understand how their sex uniquely affects their body’s response?

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