Two masks may be better than one, CDC study finds

By ANNE FLAHERTY, ABC News

(NEW YORK) — Fit matters when it comes to your mask protecting you against the virus that causes COVID-19, and layering a well-fitting cloth mask over a surgical mask is likely to prove beneficial, according to new findings to be released Wednesday by the Centers for Disease Control and Prevention.

The findings, which will be released by The Journal of the American Medical Association, were not expected to lead to new mask recommendations by the CDC. The public health agency maintains that everyone should wear a face covering when outside their home.

It also doesn’t change the recommendation that primarily medical workers in high-risk environments should rely on N95 masks, which act as a strong filter against any contaminants but is notably tougher to breathe in and withstand for long periods of time.

Still, the experiment touches on some of the big questions Americans have on how best to protect themselves when mixing in public, such as grocery stores and airplanes.

The research suggests that when a person “double masks” — wearing a polypropylene surgical mask with a cloth mask on top — and the people around them did the same, the risk of transmitting the virus falls more than 95%.

Researchers, who used two mannequin-like forms to test exposure, found a similar benefit with tightening a single surgical mask around the ears to improve its fit. Using a hack known as a “knot and tuck,” the researchers ensured the surgical mask fits closely around the face without gaps.

The benefit, though, fell to 80% if only one person wore the double mask and 60% if only one person knotted their surgical mask for a tighter fit.

Dr. John Brooks, chief medical officer for the CDC’s COVID-19 emergency response, said the research results make the case that “community masking” — everyone wearing a mask and not just a few people — matters.

The study also suggests that combining the close-fit of a cloth mask with the filtration of a surgical mask is a good option, he said.

“Universal masking is one of our most potent interventions to control the pandemic, we believe,” Brooks told ABC News in an interview.

“When all of us mask, not only does it giving us some personal protection. But by each of us doing that, we’re protecting other people,” he added.

In recent weeks, the CDC has been pressed on whether it might toughen its recommendation on masks and possibly embrace N95 masks for public use now that hospitals and medical workers have an adequate supply.

But agency officials have declined to suggest specifically that Americans wear the tight-fitting N95s because — while highly effective — they are particularly difficult to wear for long periods of time because they are harder to breathe in.

Also, CDC Director Rochelle Walensky has said wearing an N95 mask probably isn’t necessary in public places.

“I think if everybody is wearing a mask, if you’re wearing it and six feet apart … you have enough protective effectiveness in the barriers of those two masks and the space between you that you probably don’t need it,” Walensky said Jan. 27 during a CNN Town Hall.

Brooks cautions that people shouldn’t read too closely into the specific efficacy numbers from the experiment. Researchers didn’t experiment with different types of cloth materials and other combinations might be just as useful. Brooks said other options might be using “mask fitters” and a nylon hosiery sleeve.

But the research demonstrated the principle that when the fit is improved, that improves the overall efficiency of how the mask performs. And if the mask is better at stopping the virus, that in turn can prevent viral mutations that threaten the efficacy of vaccines.

“We want to communicate to the public that if you want to get more out of that mask, there’s a number of low-tech ways you can improve its performance,” he said.

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