Women are more likely to develop a stronger immune response to the novel coronavirus compared with men, a new study has found, offering a possible explanation for the more severe illness of COVID-19 often observed in men.
The findings published in the journal Nature on Wednesday noted that globally, men account for about 60 percent of COVID-19 related deaths – the highly infectious respiratory disease caused by the new coronavirus.
“What we found was that men and women indeed develop different types of immune responses to COVID-19,” said Akiko Iwasaki, the study’s lead author and a professor at Yale University in the United States.
The immunity specialist said “these differences may underlie heightened disease susceptibility in men”.
Researchers collected nasal, saliva, and blood samples from non-infected control subjects and patients with the disease who were treated at Yale New Haven Hospital in the United States.
They found that women mounted a more robust immune response involving T lymphocytes, which are a type of white blood cell that can recognise viruses and eliminate them. This was the case even among older women, the study found.
In contrast, older men had weaker T cell activity – the older they were, the weaker the response.
Overall men also produced more cytokines, which are inflammatory proteins that form another part of the body’s natural immune defence.
However, severe cases of COVID-19 have been linked to what is known as a “cytokine storm”, when the immune system goes into overdrive, which is harmful and potentially deadly.
Men who showed high concentrations early on were more likely to have a severe case of the disease, while those women who also showed significant cytokine levels appeared to fare worse, the study found.
According to the authors, this could imply that men and women need different treatments.
For men, for example “we should be enhancing their T cell responses with vaccines”, Iwasaki said, while women could be given treatment to dampen the cytokine response.
Since the start of the pandemic, most countries have reported a higher number of deaths from the new coronavirus among men than women.
Experts have offered a number of possible explanations for this trend.
“One theory is that men are more likely to partake in unhealthy habits, which are associated with developing chronic diseases,” Dr Sara Kayat wrote in an article for Al Jazeera.
The presence of the extra X chromosome that women have as well as hormones are other possible reasons, she said.
The Yale study, which has been peer-reviewed, has some limitations, however. The sample size was relatively small, with 98 patients in total. The average age of the patients was also high, at about 60 years.
Commenting on the research, Eleanor Riley, a professor at the University of Edinburgh, said some of the divergence noted in the study is likely caused by differences in age or BMI, which measures body fat. The sex differences disappear once these other factors are taken into account.
She said treatments would be better if they were individually tailored, rather than defined solely based on sex.