Wearing a mask can help protect you when no one else is wearing one

A federal judge in Florida on April 18 overturned the U.S. Centers for Disease Control and Prevention (CDC) mandate for a public transit mask, meaning people no longer need to wear masks on public transit in most cases. .

With the mandates ending, some public health experts have advised people to continue masking on public transport and other crowded indoor spaces, even if others around them aren’t. People at high risk for severe COVID-19 — including those who are immunocompromised or have chronic conditions — may want to continue wearing a high-quality mask, even if it’s not recommended for everyone in their area, under the guidance of the CDC.

But is “one-way masking” — or wearing a mask even when no one else around you does — really enough to protect you from being infected with SARS-CoV-2, the virus that causes COVID-19?

“One-way masking is definitely better than nothing,” says Emily Sickbert-Bennett, director of infection prevention at UNC Medical Center, but she says it’s also not as good as universal masking.

A mask should work in two different ways: by trapping the wearer’s germs and filtering out other people’s germs. If two people wear masks that catch some of the particles they exhale, there are likely to be fewer germs floating in their shared air, and both people are less likely to get sick. “One of the most important things you want to do in infection control is to block the source,” said Kimberly Prather, an aerosol expert and chair of atmospheric chemistry at the University of California, San Diego. “Never let it air in the first place.”

If one person is unmasked and exhales germs freely, the protective burden rests entirely on the other person’s mask. While fabrics and surgical masks provide some protection in this scenario, respirators such as N95s and KN95s are designed to filter out almost all particulates, making them the best and most protective options for one-way masking.

A pilot study published in the journal PNAS in December 2021 estimated the likelihood of a masked person getting sick after talking to an unmasked person who has COVID-19. Someone wearing a surgical mask had up to a 90% chance of becoming infected after half an hour (even while sitting about five feet from the sick person), while someone wearing a respirator had about a 20% chance after a full hour, the researchers estimated. If both the patient and his companion wore respirators, the infection risk dropped to just 0.4% after one hour.

In other words, wearing a high-quality mask offers significant protection even when others aren’t wearing one, but two-way masking is even better, the study suggests.

A relatively small CDC study published in February provides some real-world data. It found that people who said they always wore respirators in indoor public settings were 83% less likely to test positive for COVID-19 later, compared to people who said they didn’t wear a mask indoors. People who wore surgical masks were 66% less likely and people who wore cloth masks were 56% less likely to test positive. Of course, someone who wears a gas mask in public is probably more cautious about COVID-19 than someone who goes indoors unmasked — and the data is self-reported — but the CDC authors still concluded that masks help prevent people wearing them. wear, get sick.

Read more: What to do if you test positive for COVID-19 while traveling

Respirators such as N95s are the most protective masks on the market, but they only work optimally if they fit properly. Your respirator should create a tight seal on your face, with no openings to let in air. (Experts say a good way to test this is to hold your hands to your face and breathe in and out. If your mask fits properly, you shouldn’t feel any air escaping.)

There are also many counterfeit masks for sale, so be careful when buying. Packaging for genuine N95s is marked with an approval label from the National Institute for Occupational Safety and Health (NIOSH). The nonprofit Project N95 also has guidelines for finding authentic respirators, and a White House website directs people to where to find free N95 masks in their area.

If you don’t want to wear a respirator but still want to wear a mask in public, you can make a surgical mask more effective with a few simple adjustments, says Sickbert-Bennett. Tie the ear loops for a tighter fit and use the metal nose clip to help the mask conform to the contours of your face. (Sickbert-Bennett recommends using both hands to smooth the bar on either side of your nose rather than squeezing it, which can create a point on the bridge of your nose that lets air in.) If you’re wearing a cloth mask. want to wear, layer over a surgical mask for extra protection.

Read more: Which airlines and other transit services still need masks?

Aside from staying on top of COVID-19 vaccinations, “having a well-fitting mask is the best thing you can do” to protect yourself in indoor public settings, Sickbert-Bennett says. But it is not infallible. When you’re around someone with COVID-19, many factors can influence whether or not they become infected: how contagious they are, whether they are masked, how much protection you have against vaccines and previous exposures, how strong you are. immune system, and so on.

While one-way masking isn’t perfect, Dr. Monica Gandhi, associate chief of the University of California, San Francisco’s Division of HIV, Infectious Diseases and Global Medicine, said it is an appropriate strategy now that highly effective vaccines and boosters are widely available in the U.S. and therapies are available for people who do not respond well. on vaccination.

Mask mandates have turned out to be imperfect, Gandhi says. Some people wore masks incorrectly or not at all, while others (initially at the behest of U.S. public health officials) chose lower-quality cloth masks. She argues that it is time to acknowledge those shortcomings, move away from mandates and instead encourage people who want extra protection to wear high-quality respirators.

But the most vulnerable members of society may be at increased risk of infection with masks turned off in most shared indoor spaces. Children under the age of 5 cannot yet be vaccinated, and older people and people with reduced immunity may still be careful not to get infected. “It’s a much bigger burden now for the high-risk individuals,” Prather says.

Prather says she would be more comfortable ending mask mandates if the U.S. had better standards for measuring indoor air quality, properly ventilating spaces and filtering indoor public air. Cleaner indoor air could act as “a mask for the whole room,” reducing or even eliminating individuals’ need for real masks, she says.

Until and unless that happens, wearing a high-quality mask in indoor areas is a good way to protect yourself, even when others aren’t.

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Write to Jamie Ducharme at jamie.ducharme@time.com.

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