This Popular Type of Mask May Not Do Anything to Protect You, New Study Says
Researchers found that this mask was notably less effective than others.
For many of us, masks have become something we never leave home without these days. Before a COVID-19 vaccine was approved and available, masks were touted as our first line of defense against the virus, in addition to social distancing and good hand hygiene. While surgical masks and N95 respirators were always considered to be some of the more protective options, many of us leaned on cloth masks to do the trick. But now, a new study shows they may not be offering sufficient protection against COVID-19.
The new study, which is currently being peer reviewed for publication in the journal Science, was posted online on Aug. 31. In an effort to examine the effectiveness of masks against the spread of COVID, the researchers tracked more than 340,000 adults in 600 villages in rural Bangladesh. The findings of the research, which is the largest randomized study on the subject to date, showed that masks significantly limited the spread of the virus. Overall, the researchers saw a 9.3 percent reduction in symptomatic COVID cases and an 11.9 percent reduction in the prevalence of COVID-like symptoms once slightly under half of people—42 percent—wore masks. "The total impact with near-universal masking—perhaps achievable with alternative strategies or stricter enforcement—may be several times larger than our 10 percent estimate," the study authors note.
Jason Abaluck, PhD, an economist at Yale University who helped lead the study, told The Washington Post that the findings should be a "nail in the coffin" of any arguments against masking. "I think this should basically end any scientific debate about whether masks can be effective in combating COVID at the population level," he said.
While the study made researchers even more confident in masking as a virus-fighting measure, it showed that not all masks are created equal. The study authors note that while they found "clear evidence" that surgical masks are effective at reducing symptomatic COVID, they couldn't say the same for cloth masks. The filtration efficiency with surgical masks was 95 percent, according to their findings, but only 37 percent among cloth masks. The study found that the villages that received surgical masks saw a relative reduction of symptomatic COVID by 11 percent overall, 23 percent among people between the ages of 50 to 60, and 35 percent among those over 60.
The surgical masks used for the study had three layers of 100 percent non-woven polypropylene, while the cloth masks used had an exterior layer of 100 percent non-woven polypropylene on top of two interior layers made up of a combination of cotton and polyester interlocking knit. "While cloth masks clearly reduce symptoms, we cannot reject that they have zero or only a small impact on symptomatic COVID infections," the authors wrote in their findings, leading the researchers to advocate for the use of surgical masks over cloth ones. "Surgical masks have higher filtration efficiency, are cheaper, are consistently worn, and are better supported by our evidence as tools to reduce COVID-19."
However, Abaluck said the study doesn't necessarily prove that cloth masks should be counted out. The research doesn't "necessarily show that surgical masks are much, much better than cloth masks, but we find much clearer evidence of the effectiveness in surgical masks," he explained.
In recent weeks, the conversation around cloth masks being less effective than other masks has led some European airlines to ban them and some governments, like Austria and Germany, to mandate medical-grade masks in public, Fast Company reports. A recent study published in the journal Physics of Fluids in late July found that basic cloth masks had a filtration efficiency of 9.8 percent. Meanwhile, the research showed that surgical masks saw a slightly higher filtration efficiency of 12.4 percent. N95 and KN95 masks, however, were much more efficient, with rates of 60 percent and 46 percent, respectively. The researchers behind the July study say it may not be the masks themselves, but rather the poor fit of most cloth and surgical masks that makes them less protective.
Public health experts agree that everyone should consider the kind of masks they're trusting to protect them COVID, especially as the more contagious Delta variant has taken over. During an interview with CNN in early August, Michael Osterholm, PhD, epidemiologist and director of the University of Minnesota Center for Infectious Disease Research and Policy, said some masks, specifically cloth ones, aren't up for the challenge of preventing the spread of COVID. "We know today that many of the face cloth coverings that people wear are not very effective in reducing any of the virus movement in or out," he said before pointing to N95 respirators as the best bet.
While public health experts originally told people in the U.S. to reserve N95s for medical professionals, they're now more readily available. Osterholm says N95s "would do a lot for both people who are not yet vaccinated or are not previously infected, protecting them as well as keeping others who might become infected …. from breathing out the virus."
Similarly, during a late July appearance on CBS's Face the Nation, Scott Gottlieb, MD, the former Food & Drug Administration commissioner, said that a high quality mask is necessary to protect against the now dominant Delta variant. "It's not more airborne, and it's not more likely to be permeable to a mask. So a mask can still be helpful," Gottlieb said. "I think, though, if you're going to consider wearing a mask, the quality of the mask does matter. So if you can get your hands on a KN95 mask or an N95 mask, that's going to afford you a lot more protection."