New research suggests that women’s biological differences from men may give them an advantage when it comes to COVID-19 survival.

While vaccines can offer people protection against COVID-19, there are other risk factors such as a person’s sex that are uncontrollable. Centers for Disease Control and Prevention data show nearly 20% more men dying from COVID-19 than women (517,016 male deaths versus 417,130 female deaths) between 2020 and 2022. 

Researchers say this difference may be partly due to the influence of the female hormone estrogen on immunity.

Estrogen Linked to Decreased Likelihood of Death from COVID-19

In a study published February 14 in BMJ Open, researchers from Sweden examined national health registry data on 14,685 women aged 50 to 80 years old. The women had tested positive for COVID-19 in 2020, and most had experienced menopause when estrogen levels typically decline. About 17% of the women were using some kind of medication that affected estrogen levels, which the researchers were most interested in observing:

• Two hundred twenty-seven (277) women were taking endocrine therapy, a breast cancer treatment that reduces estrogen.
• Two thousand five hundred thirty-five (2,535) women were taking estrogen replacement to ease menopausal symptoms.
• Eleven thousand nine hundred twenty-three (11,925) remaining women made up the control group.

Once external factors like age and co-conditions were accounted for, women taking estrogen replacement, which raises estrogen levels, were about 50% less likely to die from COVID-19 than women not taking estrogen therapy. (No significant difference between women taking estrogen-lowering medication and controls was found.)

Findings Support Other Research

Dr. Franck Mauvais-Jarvis, who directs Tulane University’s Sex-Based Medicine Laboratory, says this link of elevated estrogen with lower risk of severe COVID-19 aligns with other research. Experts theorize that estrogen, and to some extent progesterone, have a role in immunity and may prevent inflammation from initiating a dangerous overreaction by the immune system called a “cytokine storm.’

Dr. Malin Sund, co-author of the Swedish study, said other research suggests that estrogen may also interfere with spike protein receptors on SARS-CoV-2 that allow the virus to enter cells.

That said, Malin notes that randomized clinical trials are needed to measure hormone levels over time, establish whether this link between estrogen and COVID-19 illness is causal, and then whether estrogen treatment can provide protection.

A Word of Caution

Until researchers know more, Sund cautions people against increasing estrogen levels, which can have side effects like increased breast cancer risk. At the same time, she says women who’ve had breast cancer “should absolutely not stop taking their endocrine therapy based on this study because they really need their treatment for breast cancer.” Instead, she advises vaccination for protection.

Studying disease differences between men and women wasn’t always done in research, and it shouldn’t end with COVID-19, Mauvais-Jarvis says.

*Law, T. (2022, February 18). Women Seem to Have Better COVID-19 Outcomes Than Men. Here’s a Theory Why. Time. https://time.com/6149597/women-covid-19-estrogen