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COVID-19

School of Public Health Expert Insights

Sabra Klein in COVID lab

Why COVID-19 Hits Men Harder

By Michael Hughes | May 4, 2020


Statistically, men are more likely to face severe consequences from COVID-19 than women are.

In fact, a new Frontiers in Public Health study of cases in China found that men are 2.4 times more likely to die from COVID-19. And a recent JAMA study showed that among all hospitalized patients in New York City, men were significantly more likely to die from COVID-19 than women at every 10-year interval over the age of 20.

Why are men more vulnerable? And are the differences more biological or behavioral? Virologist Sabra Klein, PhD ’98, MS, MA, who studies sex differences and immune response to viruses and vaccines, says the answers aren’t yet clear. Possible reasons could include women’s stronger immune systems and men’s less frequent handwashing and greater propensity to smoke and drink, says Klein, a professor in Molecular Microbiology and Immunology at the Bloomberg School.

The following Q&A is adapted from on the Public Health on Call podcast “Are Men More Susceptible to COVID-19?” Klein discusses the issues in full with Rosemary Morgan, PhD, MSc, an assistant scientist in International Health, and interviewer Stephanie Desmon, director of media and public relations for the Johns Hopkins Center for Communication Programs.

The Takeaways

  • Men and women are infected with the novel coronavirus at similar rates, but men are more likely to be admitted into intensive care and to die. It’s not clear why this is.
  • Women have stronger immune responses in general. That can mean better immunity but also risks when the response is too strong.
  • Another possible reason why men experience more severe COVID-19 reactions: They are more likely than women to have other diseases like diabetes, hypertension, and cardiovascular disease.

Why do men seem to be dying more than women from the coronavirus?

The honest truth? We don't know. At the moment, across diverse countries around the world, what we are consistently finding is that while we do not see differences between men and women in the number of cases, there is a significant male bias in admission into ICUs—as well as in mortality.

So being male is a risk factor for more severe outcomes during this pandemic. And we really don't fully understand why.

Could the difference in severity and outcomes be biological?

One difference is the greater immune responses that we typically see in females as compared with males. This greater immunity can be a blessing or it can be a curse.

How could the greater immune response in women be protective?

In many cases those immune responses are critical for recognizing that the virus has entered the body and for initiating the subsequent responses that are important for clearing the virus from our body.

How could it be harmful?

A robust immune response is associated with the “cytokine storm,” an increased number of proteins being produced by our immune system in response to the infection, which can sometimes cause disease. Detrimental outcomes from infection can be caused by our immune system exhibiting too robust of a response to the presence of the virus.

Are there behavioral differences between men and women that could be contributing to the disparities?

While we still need more data, we do know there are differences in some countries, such as smoking rates between men and women. In China, a lot more men smoke than women.

We see data around handwashing, too—how men are less likely to wash their hands. And we also know behavior links to biology about comorbidities. Men with diabetes and high blood pressure often engage in behavioral activities that put them more at risk, like smoking, drinking, and bad eating habits.

Do men have more comorbidities?

Men suffer from more comorbidities—diabetes, hypertension, cardiovascular disease—than women do. Testosterone in men, for example, can play a role in the development of hypertension.

Does age play a role?

The sex difference has an interaction with our age. We found during the 2009 flu pandemic that during our reproductive years—in people who were roughly 18 to 50 years of age—it was women who actually suffered more severe outcomes.

Is estrogen a factor?

As women enter menopause, and estrogen lowers, we start to see a reduction in immunity in females. And that drop in immunity seems to, in some cases, protect us from the inflammation that can be initiated by infection.

Michael Hughes is communications manager for the Center for Alternatives to Animal Testing at the Bloomberg School.