A new report from the Centers for Disease Control and Prevention (CDC) said masks not only protect the general public from COVID-19, but also protect the mask wearer.
In its strongest endorsement to date about the effectiveness of masks, the CDC said "adopting universal masking policies can help avert future lockdowns, especially if combined with other non-pharmaceutical interventions such as social distancing, hand hygiene, and adequate ventilation."
CDC said the data regarding the “real-world” effectiveness of community masking are limited to observational and epidemiological studies, but seven separate studies have confirmed the benefit of universal masking.
CDC also cited an analysis by Goldman Sachs from June, which found that increasing universal masking by 15 percent could prevent the need for lockdowns, and reduce associated losses of up to $1 trillion or about 5 percent of gross domestic product.
Health experts have said defiance of advice to wear masks is a key reason the U.S. infection rate exceeds that of almost every other nation. There are now more than 10 million COVID-19 infections in the country, and some governors are still resisting mask mandates.
The SARS-CoV-2 virus spreads mainly through respiratory droplets in the air, particularly when people are coughing, sneezing, talking or even breathing.
Masks are intended to reduce the amount of droplets expelled into the air, especially for asymptomatic or presymptomatic people who feel well and may be unaware they are infected. The CDC said these people account for more than 50 percent of all transmissions.
Ever since CDC first recommended widespread mask usage in April, the reasoning was to protect other people —when everyone in public wears a mask, everyone can be protected.
But on Tuesday, the CDC said masks also help reduce inhalation of droplets by the wearer.
"Studies demonstrate that cloth mask materials can also reduce wearers’ exposure to infectious droplets through filtration, including filtration of fine droplets and particles less than 10 microns," the agency said in a brief.
Further research is needed to identify the combinations of materials that maximize both their blocking and filtering effectiveness, CDC said.
However, studies are conclusive that multiple layers of cloth with higher thread counts are significantly better than single layers of cloth with lower thread counts. In some cases, CDC said, such masks filtered nearly 50 percent of fine particles smaller than 1 micron.
For comparison, experts say the virus itself is about 0.12 microns in diameter, and an N95 mask protects down to 0.1 microns.