Paris (AFP)

The immune response of women against Covid-19 could be stronger than that of men, which could explain why the latter are more affected by serious forms, suggests a study published Wednesday.

"What we have found is that men and women develop different types of immune response to Covid-19," said lead author of the study, Prof. Akiko Iwasaki, in a video uploaded by his Yale University (United States).

According to this immunity specialist, "these differences may imply an increased susceptibility of men to this disease". Published in the scientific journal Nature, the study recalls that "men represent 60% of deaths from Covid-19 in the world".

According to this work, the action of T lymphocytes (which kill infected cells and are thus responsible for one part of the immune response) was stronger in women than in men among the patients examined.

And unlike men, women could develop a strong T cell response even when they were older.

For their part, at an early stage of infection, men generally produced more cytokines than women.

However, it is the excessive and uncontrolled production of these substances, caused by a runaway immune system, which is singled out in severe forms of Covid-19 (this is called a "cytokine storm").

The authors of the study observed that in men, a poorer T cell response was an aggravating factor for the disease. And the older the men, the weaker this response.

On the other hand, women who had a high level of cytokine at the onset of infection were those whose condition worsened later.

According to the researchers, these results could lead to differentiating treatments according to gender.

For men, "we should improve the response of T lymphocytes via vaccines," said Professor Iwasaki. For women, it would be more about "blocking the cytokine response".

However, this study has limitations.

First, it is based on a small number of patients: 17 men and 22 women who should not have been placed in intensive care or have received drugs acting on the immune system (plus 59 other patients who did not meet these criteria, for a larger sample).

In addition, the average age was high (around sixty years).

"Several of the differences observed could be due to age or body mass index" or even "chance", rather than gender, believes a specialist who was not involved in the study, Pr Eleanor Riley (University of Edinburgh), cited by the British organization Science Media Center.

In addition, "although the average response differs" between the group of men and the group of women, at the individual level, many men and women have similar responses, she continues.

This is why treatments should rather be individually tailored to each patient and not defined solely by gender, she believes.

© 2020 AFP