Skip to Content
Pandemic protection

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

We answered five big questions about the new covid guidance in the US, which recommends masks in some public places.

Test and Trace Corps walk the streets of Brooklyn passing out masks
Test and Trace Corps walk the streets of Brooklyn passing out masks
Spencer Platt/Getty Images

On Tuesday, July 27, the US Centers for Disease Control and Prevention recommended that vaccinated people wear masks in public indoor spaces in communities where covid cases are spiking.

Along with the new policy, the CDC recommends that children in grades K–12 attend school in person while continuing to wear masks inside. 

Why is the CDC making this switch?  

The announcement comes on the heels of rising infections with the delta variant, the highly infectious strain of covid that was first detected in India earlier this year. The new policy may seem like backtracking, but Rochelle Walensky, director of the CDC, explained that the agency’s decisions aren’t made lightly.  

“Our guidance and recommendations will follow the science,” said Walensky during a press briefing. “The delta variant is showing every day its willingness to outsmart us and to be an opportunist in areas where we have not shown a fortified response against it.” 

In May, delta was responsible for just 2% of cases sequenced in the US, but today 82% of samples contain the more contagious variant, according to Johns Hopkins

Does this change affect me?  

Probably (if you live in the US). More than 63% of the US is experiencing what the CDC calls “substantial transmission rates,” which means the new policy would apply there. To find out if you’re living in an area where covid is surging, visit the CDC’s Covid Data Tracker, which tracks infections by county.  

(If you’re not fully vaccinated, this may not be much of a change, depending on where you live. Eight states, including California, New York, and Nevada, have already been requiring unvaccinated people to mask up.) 

How is the delta variant spreading?  

The CDC believes that unvaccinated people are driving this spread. But rarely, vaccinated people are also getting sick and may be passing on the infection, although their cases are likely much less severe. Earlier in the pandemic, a person with covid could infect 2.5 others, on average. But with the delta variant, one infection spawns an average of six more. 

“That means it doesn’t take a lot of close contact time—seconds versus minutes—for the virus to spread from one person to another,” says Ajay Sethi, a professor at the University of Wisconsin who studies infectious diseases.  

Who's protected by this new mask guidance? 

Walensky said the new mask policy is about protecting some of the most susceptible people in our society, like those who live in high-transmission areas or who have vulnerable family members like children or people with preexisting health issues. 

She also said it was important for the US to get control of the spread quickly because a future variant could evade the vaccine’s efficacy in terms of preventing severe disease and death.

That doesn’t necessarily make the changes easier for the public to accept. 

“Unfortunately, many people will see this as a flip-flop, particularly those already critical of the CDC,” says Sethi.  

What next? 

Sethi says that although the public desperately wants to believe the pandemic is over, it won’t be as long as health policies are being ignored. 

Walensky stressed that the US vaccination rate must improve, and quickly. She said: “This moment, and most importantly the associated illness, suffering, and death, could have been avoided with higher vaccination coverage in this country.”  

She also made no promises that the guidance won’t change once more: “We continue to follow the science closely, and update the guidance should the science shift again.” 

Deep Dive

Pandemic Technology Project

Kirsch funds fluvoximine research
Kirsch funds fluvoximine research

This tech millionaire went from covid trial funder to misinformation superspreader

After boosting unproven covid drugs and campaigning against vaccines, Steve Kirsch was abandoned by his team of scientific advisers—and left out of a job.

What’s happening with covid vaccine apps in the US

The world is debating apps that prove you've been vaccinated. We're keeping track of what you really need to know.

vaccine credetialing concept
vaccine credetialing concept

What you need to know about US vaccine proof on your phone

How and where you may need to show digital vaccine proof—and what the bigger picture looks like for covid credentials and apps.

limitations of facial recognition concept art
limitations of facial recognition concept art

The pandemic is testing the limits of face recognition

Government use of face ID systems exploded during the pandemic—but tying it to critical services has left some people locked out at the moment they needed help the most.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at with a list of newsletters you’d like to receive.