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CDC Urges Most Vaccinated People to Mask Up Indoors

New data on the delta variant show even vaccinated individuals can spread the virus

Signs inform visitors that masks are required inside the Ferry Building in San Francisco, California, U.S., on Monday, July 19, 2021.

Bloomberg/Getty Images

En español | Two months after announcing that vaccinated Americans can, for the most part, go mask-free, U.S. health officials are now recommending that they mask up in some circumstances.

Teachers, students, staff and visitors are advised to wear masks in schools throughout the U.S., regardless of vaccination status, the Centers for Disease Control and Prevention (CDC) announced on July 27. And vaccinated individuals who live in or visit areas of substantial or high COVID-19 transmission — which is currently about three-fourths of the country — should also wear masks in public indoor settings. (You can check the CDC's website for a county-by-county look at transmission rates to see if the new guidelines apply to you.)

Concerns over delta variant spark new guidance

The updated guidance comes on the heels of new data related to the highly contagious delta variant, which in recent weeks has been tearing through unvaccinated communities and is now responsible for more than 80 percent of new COVID-19 cases in the U.S.

This new research shows that “in rare occasions, some vaccinated people infected with the delta variant after vaccination may be contagious and spread the virus to others,” CDC Director Rochelle Walensky, M.D., said. “This new science is worrisome and unfortunately warrants an update to our recommendations.”

In fact, a study released by the CDC on July 30 found that vaccinated people infected with the delta variant have similar viral loads as unvaccinated individuals. “High viral loads suggest an increased risk of transmission,” Walensky said in a July 30 statement — meaning that while a vaccinated person may not get sick from the infection, they can still spread the virus to others, including people who are more at risk for severe illness, such as unvaccinated or immunocompromised individuals.  

The study was based on an early July COVID-19 outbreak that took place in Barnstable County, Massachusetts, a popular vacation destination better known as Cape Cod. Following multiple large public events in one town, 469 cases of COVID-19 were reported. Approximately three-fourths of cases occurred in fully vaccinated individuals; 80 percent of people with breakthrough infections had symptoms of COVID-19. No deaths were reported. The delta variant was responsible for the majority of infections.

Community Transmission of COVID-19

screen shot of the COVID-19 on the CDC website


Rates of transmission on July 28, 2021 as reported on the CDC's COVID-19 data tracker.

Visit to get current county-by-county information.

Masks return as cases rise across the country

Debate over whether mask guidance was prematurely eased has been bubbling among public health experts. When the CDC first announced in mid-May that vaccinated individuals no longer needed masks in most scenarios, COVID-19 cases had drastically decreased from the pandemic's peak in January and the delta variant was less of a concern in the U.S.

Now, COVID-19 cases are on the rise once again, and experts say the emergence of the delta variant — combined with relaxed prevention efforts and more of a return to pre-pandemic normalcy — has contributed to the virus’s resurgence. Stalled vaccination efforts haven't helped. Currently, 49 percent of the U.S. population is fully vaccinated.

"I'm very glad that the CDC is finally heeding the advice of public health leaders around the country,” Leana Wen, an emergency physician and visiting professor of health policy and management at George Washington University's Milken Institute School of Public Health, told AARP. “Back in May, I and many others feared that this exact outcome was going to happen, that the honor system would not work, and that we would have surges. Now with the delta variant, we have to have masking restrictions indoors again, unless there is proof of vaccination.”

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Walensky said in the July 27 press conference that the CDC's decision to update its mask guidance for people who are vaccinated was not “made lightly” and that she understands the fatigue and frustration many are feeling.

"We thought it was important for people to understand that they could pass the disease on to someone else,” Walensky said, especially if they live with or care for a more vulnerable individual, including young children who have not yet been vaccinated.

Vaccines remain best form of protection against COVID-19

One thing is clear from the research so far: The vaccines are still the most powerful form of prevention when it comes to COVID-19.

While mild breakthrough infections that come with symptoms similar to a cold are popping up more frequently — and likely will continue to as population-level vaccination coverage increases, the authors of the CDC study wrote — all three vaccines authorized for use in the U.S. are highly effective at preventing severe illness and death caused by COVID-19, even when it comes to the delta variant. In fact, 97 percent of all COVID-19-related hospitalizations and deaths in the U.S. are among unvaccinated individuals.

If the science shifts again, Walensky said the guidelines will, too. “We must take every step we can to stop the delta variant and end this pandemic,” she said.

Editor’s note: The article, originally published July 27, has been updated with new information.

Rachel Nania writes about health care and health policy for AARP. Previously she was a reporter and editor for WTOP Radio in Washington, D.C. A recipient of a Gracie Award and a regional Edward R. Murrow Award, she also participated in a dementia fellowship with the National Press Foundation.