Fully vaccinated people who are in areas with high or substantial COVID-19 transmission levels should wear masks in indoor public settings, the Centers for Disease Control and Prevention said Tuesday.
The recommendation was included in the CDC’s updated guidelines for people who are fully vaccinated against COVID-19. The agency also recommended universal masking at schools, and that fully vaccinated people take additional precautions and be tested after three to five days following known exposure to the coronavirus.
The mask guidance marks a change from the recommendations the agency made two months ago that said fully vaccinated Americans could resume pre-pandemic activities without wearing a face mask or social distancing, except where it is required by law, while unvaccinated people should continue to wear masks and take precautions.
It comes in response to new data that shows the highly contagious delta variant behaves differently than other strains and that, in rare occasions, vaccinated people may be able to spread it to others.
“This new science is worrisome and unfortunately warrants an update to our recommendations,” CDC Director Rochelle Walensky said during a news briefing Tuesday.
Here’s what to know about how the CDC measures COVID-19 transmission levels and how to find out if you’re in an area where the agency recommends you wear a mask even if you’re fully vaccinated.
What does high and substantial transmission mean?
The CDC defines substantial COVID-19 transmission as when between 50 and 99.99 new cases per 100,000 people have been reported over the past seven days.
High transmission is when 100 or more new COVID-19 cases per 100,000 people have been reported over the past seven days, according to the CDC.
Fully vaccinated people who are in areas of the country with either of these transmission levels are advised to wear masks when in public indoor settings.
But the CDC says fully vaccinated people may also choose to wear a mask regardless of their area’s transmission level, especially if they’re immunocompromised, at “increased risk for severe disease from COVID-19” or if they live with someone who is immunocompromised at an increased risk or not fully vaccinated.
People who are not fully vaccinated should continue to wear masks.
Where are areas of high and substantial transmission?
The CDC breaks down transmission levels by county.
Nearly 50% of counties in the U.S. have high COVID-19 transmission and nearly 17% have substantial transmission.
You can check your area’s level here. The current seven-day period is from July 20-26.
Counties with substantial transmission are marked in orange and counties with high transmission are marked in red. Areas with moderate or low transmission levels are marked in yellow or blue, respectively.
“For the most complete and up-to-date data for any particular county or state, visit the relevant health department website,” the CDC website says.