What you need to know about the CDC’s new mask guidance

The Centers for Disease Control and Prevention revised its guidance Tuesday on wearing masks to help protect against infection from the coronavirus. Under the new recommendations, the agency urges vaccinated Americans to wear masks indoors in certain circumstances.

What exactly does the revised guidance say?

Fully vaccinated or not, people who live where coronavirus transmission is classified as substantial or high should wear masks when they are indoors in public places.

The agency also called for universal mask-wearing in K-12 schools, where masks should be worn by teachers, other staff members, students and visitors. The recommendation applies to everyone over the age of 2. While vaccines are authorized for adolescents, studies are ongoing in children under age 12. And according to the CDC, just 30% of youngsters age 12 to 17 are fully vaccinated.

The CDC tracks the case rates of covid-19, the illness caused by the virus, in every county. The tracking focuses on the number of new cases per 100,000 people during the previous seven days. Substantial transmission is defined as 50 to 99 cases per 100,000 people, while high is defined as more than 100 cases per 100,000. As of Tuesday, more than 63% of U.S. counties met that definition, including swaths of the South and Midwest, up from about 46% of counties one week ago. States including Arkansas, Florida, Louisiana and Missouri are reporting “high” transmission levels across nearly every county. The CDC is recommending that vaccinated and unvaccinated people keep tabs on their county’s transmission rate to figure out whether they should wear a mask indoors in public. The tracker is here.

The CDC is not exploring the idea of recommending that all vaccinated people wear masks indoors no matter where they live or how much the virus is circulating in their community. Still, the agency now says that no matter how much virus is circulating in an area, wearing a mask is important for people at heightened risk of severe illness from covid-19 because of a weakened immune system, an underlying medical condition or advanced age.

The CDC continues to urge everyone to get one of the three coronavirus vaccines authorized for emergency use in the United States, saying the shots continue to offer a high degree of protection against becoming seriously ill. President Joe Biden is expected to announce Thursday that all federal employees will be required to be vaccinated or face testing requirements, a White House official said. The federal government can require vaccination on federal property and for its own workforce but otherwise can make only recommendations. The new mask guidance does not change vaccine recommendations.

Why did the CDC change its guidance?

The rapidly spreading delta variant of the coronavirus, which accounts for an overwhelming majority of new cases in the United States, has altered the equation considerably. During the spring, before this variant was so plentiful, research showed that fully vaccinated people were at very low risk of illness, hospitalization or death from the virus. The odds of them transmitting the virus was also thought to be very low. With delta in the picture, the CDC says, recent research from several states and other countries has shown that breakthrough infections among vaccinated people are still rare, and people who have not been vaccinated represent the bulk of the nation’s hospitalizations and deaths.

But the CDC said the delta variant is different from earlier versions of the virus, and new research, not yet published, suggests that fully vaccinated people who have breakthrough infections may have similar viral loads to unvaccinated people who become infected. That suggests that vaccinated people with breakthrough infections can spread the virus. That is the main reason the mask rules have been changed.

In addition, the change recognizes that fewer Americans are fully vaccinated than the Biden administration had hoped for by this time. In issuing its new mask guidance, the CDC continued to strongly encourage people who have balked at getting vaccinated to change their minds.

The CDC says its new advice is intended, in part, to help protect children under age 12 who are not allowed to be vaccinated and other people who have been vaccinated but are not well-protected because their immune systems are weak.

What was the previous guidance?

On May 13, the CDC announced that people who are fully vaccinated did not need to wear a mask outdoors or indoors in most circumstances. At the time, before the delta variant proliferated in the United States, research showed that vaccinated people had low risk of getting sick or spreading the virus. The Biden administration hoped that saying vaccinated people could shed their masks would motivate more people to get the shots. Critics doubted the motivational effect, pointing out that people opposed to getting a coronavirus vaccine tended to also resist wearing masks - and that it would be impossible to tell who among the newly unmasked was vaccinated.

The May guidance did not eliminate all mask requirements. Under federal rules, people still needed to wear them on planes, buses, trains and other public transportation, and they also had to observe state or local mandates on masks.

Haven’t some places begun requiring masks again on their own?

Yes. As of July 16, Los Angeles County resumed requiring people to wear masks indoors, regardless of whether they are vaccinated. The county, the nation’s most populous, with about 10 million residents, said it was responding to a resurgence of cases and to a rise in hospitalizations. But the Los Angeles County sheriff said deputies would not enforce the mandate, contending it “is not backed by science” and contradicted CDC guidance at the time. It is unclear how the new CDC advice will affect that stance.

A mask mandate also took effect again Monday in the St. Louis area. It requires everyone 5 and older to wear a mask when indoors in public places and on public transportation. The Missouri attorney general is suing to try to block the requirement.

Provincetown, Mass., revived its indoor mask mandate Sunday because of a surge of cases in the Cape Cod community after the July Fourth holiday.

So, where should I be wearing a mask?

Where you are matters. Even if you are fully vaccinated, you should put on a mask when going to a public indoor space if you are in a county where the CDC’s coronavirus tracking shows the case rate falls within the substantial or high range. And masks are recommended in schools everywhere for children over age 2 and all adults.