US Study: Double Better than Single Masking

Wearing masks plays an important role in preventing the spread of COVID-19.
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Wearing a cloth mask over a medical procedure mask can significantly decrease the spread of COVID-19, according to a new study the Centers for Disease Control and Prevention (CDC) released Wednesday.

The agency updated its guidance to note that double masking or wearing a tightly fitted surgical mask are two of the best ways to boost protection against exposure.

CDC researchers experimenting in a lab found that the better the fit of the mask, the better the protection it provides.


“The effectiveness of cloth and medical procedure masks can be improved by ensuring that they are well-fitted to the contours of the face to prevent leakage of air around the masks’ edges,” the agency said.

Double masking or knotting the ear loops of a surgical mask and tucking in the sides close to the face can reduce exposure to infectious aerosols by 95 percent, the CDC found.

The agency also said that if a medical procedure mask is worn alone, using a “mask fitter” or wearing a sleeve made of sheer nylon hosiery over either a cloth or medical procedure mask also significantly improved the wearer’s protection.

In general, any modifications to improve fit might result in equivalent improvements, regardless of the masks’ baseline effectiveness, the CDC said.

CDC Director Rochelle Walensky said the new findings do not change the agency’s overall mask guidance.


“I want to be clear that these new scientific data released today do not change the specific recommendations about who should wear a mask or when they should wear one, but they do provide new information on why wearing a well-fitting mask is so important to protect you and others,” Walensky said on a call with reporters.

“We continue to recommend that masks should have two or more layers, completely cover your nose and mouth and fit snugly against your nose and the size of your face,” Walensky added.

The agency warned to not use the study to make broad assumptions about the effectiveness of surgical masks or cloth masks.

The experiments were conducted in a lab setting, with just one type of medical procedure mask and one type of cloth mask, and the CDC cautioned they should not be interpreted as being representative of the effectiveness of these masks when worn in real-world settings.

The recommendations come three weeks into President Biden‘s term, and signal a clear effort to move past the mixed messages from the Trump administration, as deaths from COVID-19 approach 500,000.


While the CDC previously recommended people wear masks, former President Trump mocked those who did, and helped contribute to the politicization of a significant COVID-19 mitigation measure.

Experts, including the country’s top infectious diseases doctor Anthony Fauci, have been recommending double masking in recent days, especially as a way to guard against more contagious variants of the virus that are rapidly spreading.

Biden has urged all Americans to wear masks and signed executive orders requiring their use on federal property and on planes, trains and buses.

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