With the progression of the epidemic linked to the coronavirus, one thing is becoming more and more obvious: the virus affects and kills more men than women. This was noticed in China and it is also the case in one of the most affected European countries, Italy. 60% of cases of Covid-19 disease are men, the latter constituting almost 70% of deceased patients, according to the National Public Health Agency (document in Italian). This distinction between the sexes has also been observed during previous epidemics, such as those of SARS (responsible for an epidemic in 2003), as well as MERS (responsible, for its part, for epidemics in the Middle East and still active).
What is this factor?
According to Jean-Charles Guéry, who heads the Inserm research team “Immune differences related to sex: mechanisms and pathophysiology” in Toulouse: “many elements could justify this gender bias. Some are linked to lifestyle. For example, in China, men smoke more than women and also have a higher rate of type 2 diabetes and high blood pressure. Other factors are believed to be biological, with women having stronger and better quality immune responses than men in response to viral infections or vaccines ”. The reasons for this stronger immune response in women are probably multifactorial, and involve sex hormones and possibly genetic factors carried by the X chromosome that women have in duplicate and which carry many immunity genes. Sex hormones like estrogens in women and androgens in men are capable of regulating cells of the immune system.
In the case of SARS, a protective effect of estrogens
The experimental results on mice in a model of SARS infection are in favor of a positive effect of estrogens. “There is clearly a preventive effect from this molecule, continues Jean-Charles Guéry. When mice are infected with SARS, the mortality of males is much higher than that of females. When the ovaries of females are removed (and therefore the source of estrogen), or when treated with drugs that block the estrogen receptor (such as those used in the treatment of breast cancer), mortality reaches more than 80% of men. It is currently unknown whether this is a direct effect on the immune system or other tissues. “
Is it the same with the coronavirus responsible for the current epidemic?
To date, only epidemiological data in Italy and China seem to indicate this. “More research is needed in humans and animals to better understand the mechanisms responsible for this gender bias,” says Jean-Charles Guéry. But it is clear that men and women are not equal in the face of pathogens and the immune response of their organisms. With the flu virus vaccine, we know that women develop effective immunity with half the vaccine dose than men. Again, it appears that estrogen and a gene carried by the X chromosome may contribute to this increased immune response. This phenomenon fades with age, because our body manufactures less and less sex hormones as we age. After menopause, the response to the vaccine seems less good, hence, according to the researcher, the idea “that the addition of estrogens or a related supplementation to the future vaccine against SARS-Cov-2 could make it much more effective. “
Source: Sciences et Avenir