Men may have a slower immune response to the coronavirus than women, and that could explain their higher mortality rates

• Men and elderly people could be more likely to die from COVID-19 than women because they have delayed immune responses, according to a study from University of Washington researchers.
• They found that it took men's immune systems three days to kick in after being infected with the coronavirus, while women's immune systems responded more quickly.
• Their findings could explain why more men and older people have more severe COVID-19 symptoms than women.

Men's delayed immune-system responses to the coronavirus could put them at higher risk of dying from COVID-19 than women, according to a study from University of Washington researchers.

They found that, for women under the age of 60, their immune systems produced a near immediate defense against the virus. However, for men of all ages, it took an average of three days for their bodies to deploy T cells (white blood cells that sense and destroy virus-infected cells) to fight the novel coronavirus.

The researchers came to this conclusion after looking at 430 COVID-19 nasal swab tests — 176 from men and 201 from women — which they collected from the University of Washington Virology Laboratory between March and August.

This study expanded on previous research, which found women who have COVID-19 (the disease caused by the coronavirus) tend to develop more T cells, which help the body kill coronavirus-infected cells, than men who have COVID-19.

The researchers said the new findings could help to explain why nearly twice as many men have died from COVID-19 than women.

A person's sex may affect their immune response

The researchers' findings line up with previous research that suggests a person's sex affects how many virus-fighting cells a person develops when they become sick.

Females have greater amounts of the hormones estrogen, progesterone, and androgen than males, for example.

These hormones are believed to play a role in immune-system response when a person is sick.

An August study in the journal Nature found that women developed more coronavirus-fighting cells than men did, regardless of their age. For women, their age didn't affect how many cells they produced.

"We now have clear data suggesting that the immune landscape in COVID-19 patients is considerably different between the sexes and that these differences may underlie heightened disease susceptibility in men," Akiko Iwasaki, senior author of the August study, said in a press release.

The new study comes with caveats. The researchers of the new study said that their experiment should be duplicated with other bodily fluid samples, since nose swabs aren't the most effective way to test a person's immune response.

Additionally, factors like smoking and preexisting health conditions, not just a person's sex, can make them more susceptible to severe COVID-19 symptoms. Therefore, researchers can't definitively say whether sex created the delayed immune response in men.

Men and women might need different COVID-19 treatments

Still, the findings suggest men and women's bodies respond differently when they're infected, and that could mean they need different approaches to treatment too.

As Iwasaki told the New York Times, "natural infection is clearly failing" men, who tend to have worse symptoms and higher mortality rates than women when it comes to COVID-19. They might need a more doses of a coronavirus vaccine than women due to their delayed immune responses.

"You could imagine scenarios where a single shot of a vaccine might be sufficient in young individuals or maybe young women, while older men might need to have three shots of vaccine," Marcus Altfeld, an immunologist at the Heinrich Pette Institute in Germany, told the New York Times.