CDC Calls for Masks in Schools, Hard-Hit Areas, Even if Vaccinated

Damian McNamara

July 27, 2021

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The Centers for Disease Control and Prevention (CDC) once again is recommending that some Americans wear masks indoors. The agency called today for masks in K-12 school settings and in areas of the United States experiencing high or substantial SARS-CoV-2 transmission, even for the fully vaccinated.

The move reverses a controversial announcement the agency made in May 2021 that fully vaccinated Americans could skip wearing a mask in most settings.

Unlike the increasing vaccination rates and decreasing case numbers reported in May, however, some regions of the United States are now reporting large jumps in COVID-19 case numbers. And the Delta variant as well as new evidence of transmission from breakthrough cases are largely driving these changes.

"Today we have new science related to the [D]elta variant that requires us to update the guidance on what you can do when you are fully vaccinated," CDC Director Rochelle Walensky, MD, MPH, said during a media briefing today.

New evidence has emerged on breakthrough-case transmission risk, for example. "Information on the [D]elta variant from several states and other countries indicates that in rare cases, some people infected with the [D]elta variant after vaccination may be contagious and spread virus to others," Walensky said, adding that the viral loads appear to be about the same in vaccinated and unvaccinated individuals.

"This new science is worrisome," she said.

Even though unvaccinated people represent the vast majority of cases of transmission, Walensky said, "we thought it was important for [vaccinated] people to understand they have the potential to transmit the virus to others."

As a result, in addition to continuing to strongly encourage everyone to get vaccinated, the CDC recommends that fully vaccinated people wear masks in public indoor settings to help prevent spread of the Delta variant in areas with substantial or high transmission, Walensky said. "This includes schools."

Masks in Schools

The CDC is now recommending universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Their goal is to optimize safety and allow children to return to full-time in-person learning in the fall.

The CDC tracks substantial and high-transmission rates through the agency's COVID Data Tracker site. Substantial transmission means between 50 and 100 cases per 100,000 people reported over 7 days and high means more than 100 cases per 100,000 people.

The B.1.617.2, or Delta, variant is believed to be responsible for COVID-19 cases increasing more than 300% nationally from June 19 to July 23, 2021.

"A Prudent Move"

Dr Joe DeRisi

"I think it's a prudent move. Given the dominance of the [D]elta variant and the caseloads that we are seeing rising in many locations across the United States, including in my backyard here in San Francisco," Joe DeRisi, PhD, copresident of the Chan Zuckerberg Biohub and professor of biochemistry and biophysics at the University of California San Francisco, told Medscape Medical News.

DeRisi said he was not surprised that vaccinated people with breakthrough infections could be capable of transmitting the virus. He added that clinical testing done by the Biohub and UCSF produced a lot of data on viral load levels, "and they cover an enormous range."

What was unexpected to him was the rapid rise of the dominant variant. "The rise of the [D]elta strain is astonishing. It's happened so fast," he said.

"I Know It's Difficult"

Dr Colleen Kraft

Reacting to the news, Colleen Kraft, MD, said, "One of the things that we're learning is that if we're going to have low vaccine uptake or we have a number of people that can't be vaccinated yet, such as children, that we really need to go back to stopping transmission, which involves mask wearing."

"I know that it's very difficult and people feel like we're sliding backward," Kraft said during a media briefing sponsored by Emory University held shortly after the CDC announcement.

She added that the CDC updated guidance seems appropriate. "I don't think any of us really want to be in this position or want to go back to masking but…we're finding ourselves in the same place we were a year ago, in July 2020.

"In general we just don't want anybody to be infected even if there's a small chance for you to be infected and there's a small chance for you to transmit it," said Kraft, who's an assistant professor in the department of pathology and associate professor in the department of medicine, division of infectious diseases at Emory University School of Medicine in Atlanta, Georgia.

Breakthrough Transmissions

"The good news is you're still unlikely to get critically ill if you're vaccinated. But what has changed with the [D]elta variant is instead of being 90% plus protected from getting the virus at all, you're probably more in the 70% to 80% range," James T. McDeavitt, MD, told Medscape Medical News.

Dr James T. McDeavitt

"So we're seeing breakthrough infections," said McDeavitt, executive vice president and dean of clinical affairs at Baylor College of Medicine in Houston, Texas. "We are starting to see [such people] are potentially infectious." Even if a vaccinated person is individually much less likely to experience serious COVID-19 outcomes, "they can spread it to someone else who spreads it to someone else who is more vulnerable. It puts the more at-risk populations at further risk."

It breaks down to individual and public health concerns. "I am fully vaccinated. I am very confident I am not going to end up in a hospital," he said. "Now if I were unvaccinated, with the prevalence of the virus around the country, I'm probably in more danger than I've ever been in the course of the pandemic. The unvaccinated are really at risk right now."

IDSA and AMA Support Mask Change

The Infectious Diseases Society of America (IDSA) released a statement today supporting the new CDC recommendations. "To stay ahead of the spread of the highly transmissible Delta variant, IDSA also urges that in communities with moderate transmission rates, all individuals, even those who are vaccinated, wear masks in indoor public places," stated IDSA President Barbara D. Alexander, MD, MHS.

"IDSA also supports CDC's guidance recommending universal indoor masking for all teachers, staff, students and visitors to K-12 schools, regardless of vaccination status, until vaccines are authorized and widely available to all children and vaccination rates are sufficient to control transmission."

"Mask wearing will help reduce infections, prevent serious illnesses and death, limit strain on local hospitals and stave off the development of even more troubling variants," she added.

The American Medical Association (AMA) also released a statement supporting the CDC's policy changes.

"According to the CDC, emerging data indicates that vaccinated individuals infected with the Delta variant have similar viral loads as those who are unvaccinated and are capable of transmission," AMA President Gerald E. Harmon, MD said in the statement.

"However, the science remains clear, the authorized vaccines remain safe and effective in preventing severe complications from COVID-19, including hospitalization and death," he stated. "We strongly support the updated recommendations, which call for universal masking in areas of high or substantial COVID-19 transmission and in K-12 schools, to help reduce transmission of the virus. Wearing a mask is a small, but important protective measure that can help us all stay safer."

"The highest spread of cases and [most] severe outcomes are happening in places with low vaccination rates and among unvaccinated people," Walensky said. "With the [D]elta variant, vaccinating more Americans now is more urgent than ever."

"This moment, and the associated suffering, illness and death, could have been avoided with higher vaccination coverage in this country," she said.

Based on July 27, 2021, media briefings from the CDC and Emory University, as well as expert perspective.

Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology, and critical care. Follow Damian on Twitter: @MedReporter.

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