One-Way Masking Works


By Olga Khazan

If you’re vaccinated, boosted, and wearing an N95, you’re protected—no matter what others are doing. Florida, where I’ve spent the winter holidays, is now a severe-looking blackish purple on coronavirus-case-rate maps. I’ll probably get COVID any minute now, because my fellow revelers seem not overly concerned about keeping their excretions to themselves.

The other day, one young man turned his head to the side and hocked a loogie into the sand a few feet away from me. Another took a big inhale from the hookah he had brought to the beach, then puffed a cloud of apple-scented lung aerosols into the South Florida sky and, as it happens, into my nostrils as well. Indoors, I am one of the few people who wears a mask at all.

Earlier in the pandemic, this would have terrified me because, as the 2020-era mantra went, “my mask protects you, and your mask protects me.” In the Sunshine State, though, “your mask” is often nonexistent. But some researchers now think that catchphrase needs an update. Though universal masking is still safest, my mask protects me too. And wearing a good-quality mask while vaccinated and boosted (which I am) protects me pretty darn well, regardless of what everyone else is doing.

If you are vaccinated, boosted, and wearing a well-fitted N95 or similar indoors, “your risk is extremely low,” says Joseph Allen, a COVID and ventilation expert at Harvard. “I mean, there’s not much else in life that would have as low a risk as that. I would qualify your risk as de minimis.” An N95 mask filters about 95 percent of airborne particles. But two surgical masks—one on me, one on you—filter only about 91 percent, Allen wrote recently said. Because most people’s masks aren’t perfectly sealed onto their faces, studies show that N95s reduce the wearer’s uptake of coronavirus particles by 57 to 86 percent. And that’s on top of the protection that vaccines and boosters already offer.

Ideally, everyone would wear masks indoors for the next few weeks. That’s not going to happen, though. The good news is that if you’re boosted and wear a high-quality mask, you’ll probably be okay anyway. Some experts even think people who are triple-vaccinated and wearing N95s can go about their normal activities. “They should feel pretty safe because the booster provides strong protection against severe outcomes, and even if infected people are present and releasing viruses into the air, a properly fitting N95 will reduce the amount you breathe in by 95 percent or more,” says Linsey Marr, an environmental engineer at Virginia Tech who specializes in airborne transmission. “The combination of vaccination with [a] booster and an N95 provides excellent protection.”

After all, N95s were what ER doctors wore to treat COVID patients at the very beginning of the pandemic—before vaccines or boosters were available, and before most people began wearing masks indoors at all. “These masks are literally designed to block out infectious aerosols,” says Abraar Karan, an infectious-disease doctor at Stanford. He thinks that more everyday people should upgrade their masks, and that for health-care workers, N95s should be made mandatory.

The caveat is that your mask has to fit well, and it has to be an N95 or similar—cloth masks offer scant protection against Omicron. “Well fitting” means you shouldn’t have any air leakage out of the sides of the mask, near the nose, or by the chin. If you wear glasses, they shouldn’t fog up. “If you breathe in, the face piece should collapse inward just a little bit,” says Lisa Brosseau, a consultant and an expert on industrial hygiene. “If you breathe outward, you should get a little bit of expansion of the face piece.”

Unfortunately, some fashion sacrifices might need to be made: The kind of mask that’s most likely to fit you snugly is the kind with back-of-the-head straps, as opposed to ear loops, and men’s masks fit more tightly when they’re clean-shaven. Ideally, the government would set up “fit-testing booths” so people could make sure their masks fit tightly, but even the expert who suggested this idea to me acknowledged that it’s not likely. At any rate, an N95 “is still going to be better than most masks if the fit is very good as opposed to perfect,” Allen says.

Not every expert is quite this relaxed. Jose-Luis Jimenez, a professor at the University of Colorado at Boulder who studies disease transmission, told me that for the next month or so, he’s not going to go into indoor environments where lots of unmasked people are gathered. “I don’t think it can be made very safe,” he said.

Everyone I interviewed thinks it’s also important to pay attention to how crowded and ventilated a room is—Jimenez even recommends carrying around a CO2 monitor and bailing when its reading gets above 700 molecules of carbon dioxide per million. (Though, admittedly, most people do not own or carry a CO2 monitor.) The longer you spend in an enclosed space with unmasked people, the higher your risk of exposure, so a quick grocery-store run is less risky than a concert. And the extra cautious might want to avoid places where you have to take off your mask, such as indoor restaurants or bars.

The other thing to keep in mind is that personal risk—and risk tolerance—still matters. If you interact with the elderly or immunocompromised, avoiding public indoor settings entirely until this surge is over might be a good idea, even if you’re masked and boosted. And even if you are vaccinated, boosted, and wearing an N95, you might still get a breakthrough case of Omicron at, say, the movie theater right now. “If your goal is to avoid infection, which I think is possible, during the surge, your chances of being infected are so much higher than when there’s not a surge going on,” Karan says.

But healthy, boosted people are much less likely to be hospitalized for COVID-19, and they’re less likely to experience severe cases in general. At this point, if you’re relatively healthy and you’ve done everything right, you’re weighing a March 2020–style lockdown against what amounts to a mild illness. Some people might decide that they feel safe enough with an N95 to risk it.

The fact that an N95 protects its wearer, specifically, matters because we are simply not going to get every American into a mask anytime soon. Nine states—including Florida—have banned mask mandates. In many areas where masks are required, compliance is often poor because those states and localities failed to pull back on pandemic restrictions when cases were low, before Omicron hit, and “there is fatigue that sets in,” Allen says. Just like everyone began ignoring the color-coded “threat level” a few months after 9/11, people ignored mask mandates when the scourge of COVID seemed weak and the rules felt excessive. Now it’s hard to get people to take COVID seriously again.

The efficacy of one-way masking is also good news for those of us who feel that the cautious shouldn’t be forced to live at the whim of the reckless. Millions of Americans won’t accept a lifesaving vaccine, and the news about Omicron has not affected their decision. In a perfect world, everyone would mask until this surge was over. My mask would protect you, and yours would protect me. But we don’t live in a perfect world. We live in America, where denying the pandemic has become a political shibboleth; where cheap-to-make rapid tests cost $24 a pack; and where some of us want to protect ourselves, even if others don’t.


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