Public Health

Why the CDC is again turning to masks to help stop COVID-19

Kevin B. O'Reilly , Senior News Editor

What’s the news: The expert physicians and scientists at the Centers for Disease Control and Prevention (CDC) are recommending that Americans—even those who are fully immunized with one of the three safe and effective COVID-19 vaccines available in this country—wear masks in indoor public spaces if they live in areas with high or substantial rates of virus transmission.

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The masks serve as another layer of protection against transmission of the SARS-CoV-2 Delta variant that now accounts for 80% of cases in the U.S. The CDC also is recommending that children, teachers and staffers in K–12 schools across the nation wear masks in the coming school year, regardless of COVID-19 vaccination status. This brings the agency’s recommendations in line with those of the American Academy of Pediatrics.

The AMA strongly supports the scientifically driven changes.

“With cases of COVID-19 continuing to increase in the United States and a significant number of people who remain unvaccinated, the CDC’s updated mask guidance is needed to help curb the spread of COVID-19—particularly the Delta variant, which we know is much more contagious,” said AMA President Gerald E. Harmon, MD, in a statement. “Wearing a mask is a small, but important protective measure that can help us all stay safer.”

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Why it’s important: The biggest driver of the change in masking recommendation is CDC investigation of recent COVID-19 case clusters that allowed for comparison of the viral loads of unvaccinated patients who acquired SARS-CoV-2 with those fully immunized patients with breakthrough infections.

“We are seeing viral loads that are quite similar,” said CDC Director Rochelle P. Walensky, MD, MPH, during a news briefing today. Though breakthrough infections remain rare, those higher viral loads mean such infections among fully immunized patients could be transmitted to others who are unvaccinated or have compromised immune systems.

That’s a change from what the CDC found in transmission risk of the SARS-CoV-2 Alpha variant among fully immunized patients, when the agency said earlier this year that those who were vaccinated could safely go unmasked.

Dr. Walensky acknowledged the change of tune on masking is “not a welcome piece of news,” but said an array of medical and scientific experts agreed with the move. “When we show them these data, they have universally said that this is required action,” she said.

The masking recommendation change applies to areas of “substantial” or “high” transmission as noted in the CDC COVID data tracker, Dr. Walensky said. Those are areas in which there 50 or more weekly cases per 100,000 residents. Nearly two-thirds of U.S. counties are experiencing substantial or high levels of transmission.

Becoming fully immunized cuts a person’s risk of COVID-19 by sevenfold in comparison with those who are unvaccinated, she noted. Vaccination slashes the risk of COVID-19 hospitalization or death by twentyfold.

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Learn more: Throughout the COVID-19 pandemic, the AMA has urged Americans to follow the science as conditions change amid this fast-moving public health emergency. That includes urging everyone to #MaskUp to stop the spread of COVID-19 in accordance with public health recommendations.

“We still are largely in a pandemic of the unvaccinated,” Dr. Walensky said. “The vast majority of the transmission, severe hospitalization and death is almost exclusively happening in unvaccinated people. That’s why we very much want to double down and continue to get people vaccinated.”

The AMA, American Hospital Association and American Nurses Association have released a 30-second video public service announcement urging all Americans to “ask questions, follow the science and get vaccinated.” Tell patients who haven’t yet opted for SARS-CoV-2 vaccination to visit the COVID Collaborative’s website,

Also, the AMA COVID-19 vaccines guide for physicians offers evidence-based messaging guidance and best practices for consideration in external communications about the safe and effective COVID-19 vaccines that have been authorized in the U.S.