How well does one-way masking protect you from COVID?

With the decline of the omicron wave, many states are dropping their mask mandates. New York, which has been the epicenter of the pandemic on several occasions, recently dropped its indoor mask rule. Illinois does the same. Other states, including Massachusetts and New Jersey, no longer require masks in K-12 schools.

The changes are divisive, inspiring both celebration and concern from scientists, public health officials and people simply trying to get on with their lives two years into the pandemic. Omicron no longer hits the United States like it once did, but the country is still averaging more than 378,000 new cases a day. And the Centers for Disease Control and Prevention has not changed its position on public masking.

All of this raises questions about how to proceed. Should you always mask up in public, even if you live in an area that no longer requires it? Does it feel good? Here are some important points to keep in mind.

The effectiveness of one-way masking is not entirely clear…

There is no large controlled study that directly compares the effectiveness of universal masking to one-way masking in preventing the spread of COVID, largely because there are so many variables at play. What is the setting ? How is the local transmission going? What types of masks do people wear and do they fit well?

Yet doctors and researchers are pretty much unanimous that universal masking is the gold standard.

“There is no doubt that it is more effective both for the individual and for public health if a high fraction of people wear good masks when in indoor shared airspaces” , said Alex Huffman, an aerosol scientist at the University of Denver. . “Masks act as excellent source control, meaning they prevent infectious aerosol from entering the room and can significantly reduce the infectious dose the susceptible person is breathing.”

“Masks act as excellent source control, meaning they prevent infectious aerosol from entering the room and can significantly reduce the infectious dose the susceptible person is breathing.”

– Alex Huffman, an aerosol scientist at the University of Denver

The benefits that masks confer multiply when everyone in a room — that is, both the contagious person and the person who might be infected — wears a mask, Huffman explained. Thus, the infected person is less likely to spread the virus. The susceptible person is less likely to be infected. And they are therefore less likely to pass it on to each other and to anyone else they interact with.

A widely covered CDC report from last summer demonstrates the potential limitations of one-way masking in indoor group settings. A teacher in Marin County, Calif., who was exposed at times over the course of two days on the job, spread the virus to half of his students — all of whom were masked. Some of these children passed it on to their family members.

Things have changed since then, so what happens in classrooms over the next few weeks is unlikely to play out the same way. For one thing, this outbreak happened during the delta thrust. But omicron is up to four times more transmissible. On the other hand, it also took place before children between the ages of 5 and 11 were eligible for vaccines. Today they are, although overall vaccination among this age group remains low.

… But one-way masking is definitely better than nothing.

There’s a reason healthcare workers have long worn masks in many clinical settings, whether or not their patients are also masked: Masks protect the person wearing them.

So if you find yourself in a high transmission area or just aren’t comfortable unmasking indoors, you should take comfort in knowing that your mask is giving you an extra layer of protection.

“This is worth doing,” said Dr. Richard Martinello, associate professor of infectious diseases and pediatrics at Yale School of Medicine. “We have a very simple, safe and effective intervention.”

Martinello pointed to a recent CDC study that found people who wore a high-quality medical mask indoors had an 83% lower risk of contracting COVID than those who did not wear a mask indoors. He noted that it was impossible to tell if everyone around them was also masked, but said it offered even more evidence that masking prevents the spread of the virus.

Now is the time to pay special attention to the type and fit of the mask.

If you plan on continuing to hide indoors, type and fit are key, perhaps more than ever. Your first choice should be a high-quality medical mask, such as an N95, KN95, or KF94. A properly fitted N95 can filter out up to 95% of particles in the air. This recent CDC study on the effectiveness of indoor use found that cloth masks and surgical masks are much less effective at preventing the spread of COVID than these medical-grade masks.

“At this point in the pandemic, especially if you’re the only one wearing a mask, I wouldn’t bother with anything less than a very high quality respirator.”

-Alex Huffman

“The quality of the mask filter and the quality of the fit to your face matters a lot, especially if you rely on your mask to do all the heavy lifting to protect you from the virus in the air you share with others,” “At this point in the pandemic, especially if you’re the only one wearing a mask, I wouldn’t bother with anything less than a really high quality respirator,” Huffman said.

Ideally that would be an N95 or, if you’re in an environment that warrants it, the more substantial elastomeric half-mask respirators, he said. But “KF-94 rated masks are very high quality, and KN95 masks can be very good if not counterfeit,” he added. (Warning: The CDC warns that counterfeits abound. Here’s where to buy the ones that aren’t.)

“It should seal the bridge of your nose and be held in place by a small band of metal, pull tight against your cheeks and seal under your chin and jawline,” Huffman said. If possible, consider masks with headbands rather than ear loops for a better seal, he recommended.

But remember: masking is not the only defense we have in public places.

Of course, many people — including some health experts — enthusiastically welcome the decision to drop mask mandates. They point out that we have layers of protection at our disposal: we have vaccines and boosters, which reduce your risk of becoming infected and, more importantly, of becoming seriously ill if you do.

Public health experts have also learned a great deal about the importance of ventilation in indoor environments. For example, many schools have upgraded HVAC filters, added portable HEPA filtration and kept windows open, Huffman said. Handwashing, while not the most exciting of interventions, continues to be important.

These layers mean masks aren’t the only thing preventing the spread of COVID. They are all important when it comes to stopping transmission.

Experts are still learning about COVID-19. The information in this story is what was known or available at the time of publication, but advice may change as scientists discover more about the virus. Please consult the Centers for Disease Control and Prevention for the most current recommendations.




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