- Many studies show that women are less severely impacted by the coronavirus than men.
- How can this lesser vulnerability be explained? From risk factors to hormones, several hypotheses are explored. And could help move forward on treatment.
- 20 Minutes explores the various data on this “gender bias” with two researchers who specialize in this issue.
Even if the data evolves quickly and has not finished surprising us, there is information that seems fairly solid: men suffer more from this new coronavirus than women. Both in severe cases and in mortality, they are overrepresented. Several hypotheses can shed light on this “gender bias”.
Striking figures
According to a report published by Santé Publique France on April 23, since March 16, 73% of Covid-19 cases in intensive care were men. "According to the available figures, 64% of the Covid-19 deaths in Italy are men, 58% in Germany and 61% in France," underlines Jean-Charles Guéry, research director at Inserm, at the Research Center in physiopathology of Toulouse Purpan. A lag that can be read in all countries, as this graph from Statista reveals.
"This difference between men and women is not specific to this virus," explains Morgane Bomsel, director of research at the CNRS. In general, immunity in women is better in Sras, Mers and other coronaviruses. "
But also for the flu. "So when we vaccinate women, the production of antibodies is higher and of better quality than in men, adds Jean-Charles Guéry, who works on the differences between the sexes in the mechanisms of the immune system. So much so that when you vaccinate a woman with half a dose, she will have the same reaction as a man who has received a full dose. "
Risk factors more present in men
How to explain that women are less fragile compared to this coronavirus? The first assumption is based on risk factors. "The known comorbidities for this disease, hypertension, cardiovascular diseases, diabetes, affect men more than women, but also younger men," says Morgane Bomsel, a specialist in mucosal research at the Cochin Institute.
A track to qualify. Because these risk factors have left us some surprises ... On tobacco in particular. If at first, we imagined that men would die more from the coronavirus because they smoked much more than their companions (especially in China, where according to this article by TV5 Monde, 50% of men smoke against 2% of women), recent discoveries on a possible protective effect of nicotine contradict this hypothesis. Second interesting observation: a large Icelandic study, a country that has widely screened its population, has shown that even among young people, between 20 and 30 years of age, there are fewer women who are positive for the coronavirus than men. "However, young people are less likely to have co-morbidities, analyzes Jean-Charles Guéry. An argument to say that there is a biological factor which would be implied in this bias of sex. "
The hormonal track
Precisely, several specialists assure, for years, that the female hormones would have a protective effect for the health of women. Protection that would apply in general to infections and in particular to this new coronavirus. “A study published in 2017 by an American team looked at mice infected with Sars-CoV-1, for which there is no comorbidity factor. Male mice are susceptible to infection, while females resist perfectly. Neutered male mice are still as sensitive to Sars, which shows that androgens are not aggravating factors. When the ovaries are removed from the females or given a treatment to suppress the action of estrogen, they will develop a lung infection like the males. This shows that estrogens are protective. "
A long-standing discovery, but one that could prove particularly useful in the fight against the coronavirus. Two American studies were launched in late April to test these female hormones as a "treatment". In fact, in New York, a hundred patients, men and women over 55, will receive estrogen injections. In Los Angeles, progesterone will be tested, in the short term, on men with Covid. But the researchers warn: these hormones are probably not the magic potion hoped for ... Indeed, how can we explain that after menopause, even at 90, this difference between the sexes persists? "We are not born at 60, an elderly woman has accumulated an entire immune history started in utero, " says Morgane Bomsel.
Two X chromosomes
But the hormonal path is not the only one to be explored. A third hypothesis has been advanced by researchers: that of genetics. "With regard to RNA viruses (HIV, influenza, coronavirus), a gene is important for promoting an antibody response, TLR7, a gene carried by the X chromosome," specifies the Inserm researcher. However, women have two X chromosomes, men only one. This receptor will be activated to send signals and trigger an appropriate immune response. When we remove this gene from a mouse, we see poorer quality immune responses… and we see that this difference between males and females no longer exists. "
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Another strength of women: "Basically, they have more cells that produce type 1 interferons, which seem important in the immune response to the coronavirus," continues the researcher. Hypotheses that will have to be further explored and enriched before we can better understand this mysterious coronavirus.
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