In a mid-December commentary in the journal Cell on the science of mask-wearing, two experts wrote that one way for the public to get “maximal protection” from masks was to “wear a cloth mask tightly on top of a surgical mask where the surgical mask acts as a filter and the cloth mask provides an additional layer of filtration while improving the fit.”
When you combine multiple layers, “The air has to follow this tortuous path,” Linsey Marr, an expert in virus transmission at Virginia Tech who was one of the authors of the Cell commentary, told The New York Times. “The big things [like virus particles] it’s carrying are not going to be able to follow those twists and turns.”
(Another alternative suggested by the authors: A cloth mask with a pocket that can be stuffed with filter material, like the kind found in vacuum bags.)
“I recommend that people select masks based on the activity, and the level of risk for that activity. If going on a walk outdoors with a friend, a simple 2- or 3-layer mask will do,” said Joseph Allen, a professor of exposure assessment science at the Harvard T.H. Chan School of Public Health.
“If you’re going to the grocery store or you are an essential worker coming in contact with a lot of people, I recommend wearing a cotton mask over a surgical mask which can catch more than 90% of respiratory aerosols,” Allen said Friday in an e-mail. “I also like this approach because most people don’t have access to [high-filtration N95 masks], but they do have access to a cotton and surgical mask.”
On Friday, Dr. Dara Kass, an associate professor of emergency medicine at Columbia University Irving Medical Center in New York who treated coronavirus patients this spring and had the virus herself, declared her support for doubling up. “If you are in a high risk area and you are unvaccinated, double masking is the way to go,” she tweeted.
Her tweet included a photo of Pete Buttigieg, President Biden’s nominee for transportation secretary, and his husband, Chasten, wearing what appeared to be double masks at the inauguration. “Always proud to see @PeteButtigieg and @Chasten model best practices,” she wrote.
Former US Food and Drug Administrator Scott Gottlieb said Monday in a tweet, “We also need to become more vigilant about masking. Quality of mask matters more now. N95 best, or double masking.”
What can we do? We’re in a race against time to get as much protective immunity into population as backstop against continued spread. The vaccine is our only tool. We also need to become more vigilant about masking. Quality of mask matters more now. N95 best, or double masking.
— Scott Gottlieb, MD (@ScottGottliebMD) January 17, 2021
The US Centers for Disease Control and Prevention’s website doesn’t mention double-masking. The official recommendation is that people wear a mask of two or more layers of tightly woven fabric that you can’t see through, CDC spokesman Brian Katzowitz said. He noted, however, that people who only have single-layer cloth masks could double them up to get the “recommended level of protection.”
Dr. Paul Sax, clinical director of the Division of Infectious Diseases at Brigham and Women’s Hospital, sounded a similar note, saying double-masking made sense if a person only owned cloth masks that are thin.
Other experts said the new double-masking methods could help, but noted there was no research yet on the topic.
“Double masks are well-intentioned, but they haven’t been studied,” said Dr. William Schaffner, an infectious disease specialist and professor at the Vanderbilt University School of Medicine.
“If you wish to wear a double mask, I guess that’s OK,” he said in a telephone interview Friday. “It makes good common sense that you have double barriers … but make sure you put the first mask on correctly.”
“I think the main thing is to get so many Americans wearing any mask and to wear them correctly, which means including masking the nose,” he said.
Dr. Abraar Karan, a global health and internal medicine physician at Brigham and Women’s Hospital who has been an outspoken advocate for better masks, said “all these solutions are important,” but he also cautioned that double-masking wasn’t a sure thing.
“While MacGyvering your own mask at home is something that’s tempting to do and may provide protection, there’s really no guarantee,” he said in a telephone interview Friday.
He noted that for any mask, a good fit is key to getting the best filtration, and that the Cell authors had cited a better fit as one of the reasons for double-masking, with a cloth mask “tightly on top” of the typically blue surgical mask.
Karan also said the interest in double-masking highlighted the lack of high-filtration masks available to the public.
“The reason that people are trying to create these solutions is that we don’t have access to the masks that we know are already certified for health care workers,” he said.
Karan and co-authors, in an opinion column earlier this month in STAT, called for a national initiative to produce and distribute high-filtration masks like the N95s used by health care workers.
“Ideally, a set of masks would be mailed to each U.S. household every month — the costs of doing so pale in comparison to the pandemic’s toll on lives and the economy,” the column said, while calling for President Biden to use the Defense Production Act to step up production of masks.
Sax said he was also a supporter of making high-quality masks available for free or for reduced prices.
Good masks are key, experts say. A mask that is very effective at both blocking transmission of the virus by the wearer and protecting the wearer from transmission by other people will stop the virus from spreading.
It “essentially makes the wearer a dead end for the virus,” Karan said in the interview.
Now that the highly transmissible U.K. variant has reared its head in the the United States, effective masks are even more important, he said.
Material from Globe wire services was used in this report.
Martin Finucane can be reached at [email protected].