Several studies suggest that vaccines against the coronavirus may be slightly less effective in women than in men. The most recent was conducted by the CDC (Centers for Disease Control and Prevention) in the United States. They were interested in cases of Covid-19 diagnosed in people who have already been vaccinated against the virus. This is very rare since only 0.01% of Americans are concerned, relates Business Insider. But in this small portion, women represent the majority of cases (63%).
When we look at the efficacy rates of the different vaccines, we also notice that while the doses of Pfizer are 96.4% effective in men, they are 93.7% effective in women. Moderna represents an efficacy rate of 95.4% for male patients against 93.1% for women.
Estrogen levels boost the immune system
What is surprising is that usually, “male defenses react less well to bacterial, viral or parasitic infections”, sums up the media again. Futura Science. Women have stronger immune responses to vaccines, resulting in better protection. This is for example the case for measles, influenza or yellow fever. This could be explained by their higher estrogen levels which stimulate the immune system.
So how to explain that for the coronavirus, this is not the case? Nanoparticles used in RNA vaccines like Pfizer or Moderna could be the cause. These serve to protect RNA and enter cells. However, explains a specialist who conducted a study relayed by the journal Molecular Pharmacology: “We found that female dendritic cells absorb fewer nanoparticles than male dendritic cells.”
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Other factors to consider
However, scientists are keen to qualify: other factors (hormonal, chromosomal, physiological, etc.) may come into play to explain the differences in the effectiveness of the vaccine in individuals. The behaviors and prevalences of chronic diseases can also be taken into consideration.
Asked by Business Insider, Sabra Klein, co-director of the John Hopkins Center for Women’s Health, Sex and Gender Reserch, shares yet another hypothesis: “Vaccines may be less effective against variants of Covid-19 in women than in men.”
Women’s health studies
Unfortunately, deplores the scientist and other experts, studies that compare in detail the effectiveness of vaccines against Covid-19 in men and in women are very few. It is therefore difficult for the moment to obtain precise explanations.
However, “if there is one positive aspect of the pandemic for people working in women’s health, it is that it has made it very clear that it is not limited to their reproductive system.” , rejoices Sabra Klein. And to conclude: “We really have to be studied and compared to men.”
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