Scientists using computational models have reported that, in general, widespread use of facemasks, when combined with lockdowns, may help prevent future waves of infection.
Face masks have been a matter of intense debate during the COVID-19 pandemic. Early on, several government officials and health authorities were discouraging healthy people from wearing masks—noting that there was little evidence for the practice’s ability to prevent spread among the general public and citing concerns that protective face coverings, which were desperately needed by healthcare workers, were in short supply. Gradually, however, governments began to either require or recommend that their citizens wear face masks in public.
In June, the World Health Organization (WHO) recommended widespread mask-use as a way to prevent coronavirus transmission. One model estimates that if at least 95 percent of people wear masks in public between June and October, approximately 33,000 deaths could be avoided in the US.
There are three broad categories of face coverings: tight-fitting masks known as N95 respirators that are designed to filter out both aerosols (often defined as particles that are smaller than 5 micrometers in diameter) and larger airborne droplets, loose-fitting surgical masks that are fluid resistant and capable of filtering out the bigger particles, and cloth masks, which vary widely based on how they’re made.
A growing body of research supports the use of all three types of masks, though the quality of evidence varies. One of the most comprehensive examinations to date, published in The Lancetin early June, systemically assessed 172 observational studies—mostly conducted in healthcare settings—looking at the effect of physical distancing, face masks, and eye protection on the transmission of SARS-CoV-2 and two related coronaviruses. The results revealed that N95 respirators provided 96 percent protection from infection and surgical masks (or comparable reusable masks made with 12 to 16 layers of cotton or gauze) were 67 percent protective.
While research on cloth masks is much more limited, one group of researchers demonstrated that, in the lab, multilayer masks made of hybrid materials (cotton and silk, for example) could filter up to 90 percent of particles between 300 nanometers and 6 micrometers in size. However, it’s important to note this is only the case when there are no gaps around the edges of the mask, which are often present when people wear cloth or surgical masks. Indeed, the researchers’ findings suggest that gaps around any mask can reduce filtration by 60 percent or more. Still, scientists using computational models have reported that, in general, widespread use of facemasks, when combined with lockdowns, may help prevent future waves of infection.
“We’re recommending that N95s still be primarily saved for the healthcare situation,” says Kirsten Koehler, a professor of environmental health and engineering at Johns Hopkins University. “For individuals in the public, wearing a fabric mask is probably still the way to go.”
Credit: ScienceNews & TheScientist