CDC: Masks Protect the Wearer, Too

The Centers for Disease Control and Prevention (CDC) now says that masks may protect the wearer from COVID-19. That’s a slight pivot from previous messaging that stressed people should wear masks to help protect others.

The CDC made the announcement in a scientific brief released earlier this week. In the brief, the agency said that masks can provide “filtration for personal protection.”

“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 CDC says.

The agency also said the following elements are helpful in masks:

• Multiple layers of cloth with higher thread counts, which can protect against smaller droplets
• Materials like polypropylene, which may enhance filtering effectiveness by generating triboelectric charge (a form of static electricity)
• Materials like silk, which may help repel moist droplets

The CDC reiterated the importance of wearing a mask to protect others as well. “Cloth masks not only effectively block most large droplets, but they can also block the exhalation of fine droplets and particles,” the organization says. “Upwards of 80% blockage has been achieved in human experiments that have measured blocking of all respiratory droplets, with cloth masks in some studies performing on par with surgical masks as barriers for source control.”

The CDC ended the brief on this note: “Data support community masking to reduce the spread of SARS-CoV-2. The prevention benefit of masking is derived from the combination of source control and personal protection for the mask wearer. The relationship between source control and personal protection is likely complementary and possibly synergistic, so that individual benefit increases with increasing community mask use.”

Meaning, masks may offer even more benefit for the wearer when others wear them, too.

“Most of us have been waiting to see more rigorous studies and data on the use of face covering by the general public,” Amesh A. Adalja, MD, FIDSA, senior scholar at the Johns Hopkins Center for Health Security, tells Verywell. “More evidence has accumulated that show face masks not only serve as source control, but it may serve as some protection for the wearer as well.”

Stacey Rose, MD, FACP, assistant professor of medicine-infectious diseases at Baylor College of Medicine, tells Verywell that this is a “helpful summary” of the “evolving evidence that masks protect wearers.”

“Given the rising rates of infection in the United States at this time, I am hopeful that this brief will provide additional receptivity to mask-wearing among the U.S. population,” she says.

What the Research Says

The CDC cited plenty of research to back up its statements.

• A CDC study published in July found that, when two COVID-positive hairstylists and their patrons wore masks, the stylists did not transmit the virus to 67 clients who they worked on.
• A study published in April followed people who were on a long flight with two passengers who had COVID-19. Everyone wore masks, and none of the passengers or crew members tested positive for the virus in the 14 days after the flight.
• A study of 124 households in Beijing with at least one confirmed case of COVID-19 found that transmission of the virus was reduced by 79% when the patient and family members wore masks before the sick person developed symptoms.
• A retrospective case-control study in Thailand found that, of the more than 1,000 people interviewed as part of contact tracing investigations, those who reported having always worn a mask during high-risk exposures experienced had at least a 70% reduced risk of contracting COVID-19 compared to people who did not wear masks in those situations.
• A study of an outbreak aboard the military ship USS Theodore Roosevelt found that use of face coverings on-board was linked with a 70% lowered risk of contracting COVID-19.

Why Did the CDC Release This Information Now?

It’s unclear, but new data may have played a role. “The scientific brief was based in part on research that was only recently released,” Rose points out.

The CDC likes to gather as much scientific data as possible before issuing guidelines, Adalja says. “It takes time for scientific data to accumulate,” he says. “You want to have some level of confidence in the findings before you issue guidance.”

Adalja is hopeful that the new information will help increase the use of masks among the general public. “The more data that we have on how masks actually impact the trajectory of spread, the more likely people are to comply with mask recommendations,” he says. “Now that masks have been shown to be protective of the wearer also, people may be more likely to use them.”

Rose agrees. “I am hopeful—and I suspect the CDC is hopeful—that this scientific brief will help to encourage more universal mask wearing in the United States,” she says. “The demonstrable effect of such measures, both for individual risk and community risk, is increasingly clear, and we need to be doing everything we can to reduce the rate of COVID-19.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.