CDC Now Says Vaccinated People Sometimes Still Need Masks

In areas where the Delta variant is spreading widely, even vaccinated people should mask up in indoor public spaces—including in schools

Person shopping in a grocery store wearing a face mask. Photo: iStock

Just over two months after the Centers for Disease Control and Prevention relaxed mask-wearing guidelines for vaccinated people, the agency has changed course. Vaccinated people should mask up indoors in public spaces when in areas with substantial or high community spread of the virus that causes COVID-19, the agency announced at a Tuesday briefing. On Friday, the agency published new data demonstrating the possibility of outbreaks among vaccinated people, while continuing to emphasize that the risk of infection and severe illness is still far greater among unvaccinated people.

The CDC also said Tuesday that everyone in K-12 schools should wear a mask, regardless of vaccination status. And on Wednesday, the agency updated its general guidance for fully vaccinated people. Now, the CDC recommends testing for vaccinated people three to five days after exposure to a known or suspected COVID-19 case.

The updated guidance comes as the highly transmissible Delta variant spreads rapidly around the U.S., especially in areas where a higher proportion of the population is unvaccinated. Initial data suggests that the Delta variant is at least 50 percent more contagious than the Alpha variant, which was previously the most prevalent in the U.S. Alpha was already about 50 percent more transmissible than the original virus. Delta is now the most prevalent variant in the U.S., responsible for about 83 percent of new cases of COVID-19.

“The Delta variant behaves uniquely differently from past strains,” CDC Director Rochelle Walensky, MD, said on a press call announcing the new guidance. “In rare occasions, some vaccinated people infected with the Delta variant after vaccination may be contagious and spread the virus to others. This new science is worrisome and unfortunately warrants an update to our recommendations.”

More on COVID-19

Previously, the CDC relaxed COVID-19 guidelines after case rates fell and vaccination coverage increased. But with test positivity rates and cases climbing again, the agency is urging caution. According to the New York Times, the weekly average for daily new cases topped 50,000 on July 24, the first time since April.

The vaccines used in the U.S. still appear to protect against severe COVID-19 cases, said Tina Tan, MD, a pediatric infectious disease specialist and professor of pediatrics at Northwestern University, speaking at an Infectious Diseases Society of America press conference Tuesday morning. Walensky also said that “the vast majority of transmission, the vast majority of severe disease, hospitalization, and death is almost exclusively happening among unvaccinated people.”

New Guidance for Vaccinated People

The new guidance says that vaccinated people should wear masks indoors in areas of substantial or high community transmission, meaning anywhere with more than 50 cases of COVID-19 per 100,000 people over a seven-day period. You can look up transmission rates in your area using the CDC’s COVID Data Tracker.

“We have counties and states here that are now reporting over 300 cases per hundred thousand over a seven-day period, really an extraordinary amount of viral transmission,” Walensky said.

Previously, vaccinated people were asked to wear masks only when seeking healthcare; when using planes, trains, buses, and other forms of public transportation; and while in transit hubs, such as airports and train stations. Vaccinated people were also supposed to wear masks when asked by states, municipalities, or businesses. Los Angeles County, for example, had already instituted an indoor mask mandate that applies to vaccinated and unvaccinated people.

When relaxing mask guidance, the hope had been that vaccination would largely protect against any infection, Caitlin Rivers, PhD, an epidemiologist at Johns Hopkins University, said on Twitter. But it’s now becoming clear that some vaccinated people can still get infected and spread the virus, even if they are mostly protected against getting severely ill.

Masks in Schools

The CDC’s new recommendation that everyone in K-12 schools wear a mask puts the agency in line with existing recommendations from the American Academy of Pediatrics.

Right now, only 30 percent of kids 12 to 17 are vaccinated, and there are no vaccines authorized for children under 12. Vaccines are not expected to be available for younger children until this fall or winter.

The Delta variant has infected more and more children over the past month, which makes precautions in schools essential, Tan said. Returning to in-person learning is important for kids, she said, but to do so safely, protective measures need to be taken. In addition to universal mask-wearing regardless of vaccination status, that includes keeping desks at least 3 feet apart and adhering to strict social distancing, practicing good hand hygiene, grouping students and teachers into small pods, ensuring that the building has good ventilation, and establishing protocols if someone becomes ill or tests positive, Tan says.

Plus, “efforts should be made to vaccinate all individuals around these children,” she said.

New Evidence on Breakthrough Infections

The new report published Friday describes a number of breakthrough infections that were caused by an outbreak linked to a series of large public gatherings, many of them indoors, in Cape Cod, Massachusetts. The vast majority of analyzed cases were caused by the Delta variant, which—according to CDC slides leaked to the Washington Post—may be more likely to cause breakthrough infections than the original virus or other variants.

Of the 469 cases identified in the Cape Cod outbreak, 74 percent occurred in fully vaccinated people. Most of the eligible population in the area was vaccinated, so the high proportion of vaccinated people involved in this outbreak is somewhat expected, according to the report. And the vaccines still effectively protected people from severe outcomes: Of the 346 cases that occurred in vaccinated people, there were four hospitalizations and zero deaths. People showed symptoms in 79 percent of these cases, however, though researchers note that it’s possible additional asymptomatic cases were never detected.

The report also includes some explanation of why Delta may be able to spread so effectively, even among vaccinated people. When researchers collected samples from vaccinated and unvaccinated people in the Cape Cod outbreak, they found evidence suggesting that—with Delta—the viral load may be similar in vaccinated people with breakthrough infections and in unvaccinated people who get COVID-19. Previous research on earlier variants suggested that vaccinated people carried far less infectious material, making them less likely to spread COVID-19 even if they picked it up. More research is still needed to confirm these findings.

The leaked slides also assert that the Delta variant is far more contagious than the original strain, potentially as contagious as chickenpox, and that people may be contagious for longer after getting infected.

Head shot image of CRO Health editor Kevin Loria

Kevin Loria

I'm a science journalist who writes about health for Consumer Reports. I'm interested in finding the ways that people can transform their health for the better and in calling out the systems, companies, and policies that expose patients to unnecessary harm. As a dad, I spend most of my free time trying to keep up with a toddler, but I also enjoy exploring the outdoors whenever possible. Follow me on Twitter (@kevloria).