It was noticeable from the initial outbreak in Wuhan that Covid-19 was killing more men than women. By February, data from China, which involved 44,672 confirmed cases of the respiratory disease, revealed the death rate for men was 2.8%, compared to 1.7% among women.
If women are mounting a more effective immune response to Covid-19, it could be because many of the genes that regulate the immune system are encoded on the X chromosome. Everybody gets one X chromosome at conception from their mother. However, sex is determined …. by the chromosome received from their father: females get an additional X, whereas males do not …. According to The Better Half by American physician Sharon Moalem, having this second X chromosome gives women an immunological advantage. Every cell in a woman’s body has twice the number of X chromosomes as a man’s, and so twice the number of genes that can be called upon to regulate her immune response, he says. Only one of the X chromosomes in each cell will be active at any time, but having that diversity of options gives women a better immunological toolbox to fight infections.
Moalem describes the possession of XX chromosomes as “female genetic superiority”.