The Biden administration said Tuesday there’s no need for people who are vaccinated against COVID-19 to wear face masks while outdoors unless they are in crowded, large-group settings.

Fully vaccinated individuals do not need to wear a mask when exercising outdoors or attending small and medium-sized outdoor gatherings, according to new Centers for Disease Control and Prevention guidance. CDC Director Rochelle Walensky pointedly did not define how many people constitute a small or medium-sized gathering because that can depend on the space, how much distance separates people and local COVID-19 caseloads.

She told reporters it is also safe for fully vaccinated people to dine at an outdoor restaurant with vaccinated friends from multiple households while not wearing masks.

Walensky said most virus transmission currently happens indoors, with less than 10 percent of virus transmission traced to outdoor exposures. 

Unvaccinated people should still wear a mask when attending a small outdoor gathering with other unvaccinated people to reduce the risk of severe disease, Walensky said. But an unvaccinated person can feel safe walking, running or biking outdoors without a mask on.

The CDC also says it’s now safer for vaccinated individuals to attend certain indoor events with a mask on because of increased vaccination rates and decreased community spread. A fully vaccinated person wearing a mask can feel safe attending a worship service and singing in the choir, visiting a hair salon, shopping indoors, visiting a museum, riding public transportation, participating in an indoor exercise class or going to a movie theater.

A person is fully vaccinated two weeks after receiving a second dose of the Pfizer or Moderna vaccines that were authorized in the United States, or two weeks after getting the one-shot Johnson & Johnson vaccine. 

President Joe Biden touted the guidance as a sign of the success of the U.S. COVID-19 vaccination program and called on more Americans to get the shot.

“The bottom line is clear. If you’re vaccinated, you can do more things safely, both outdoors as well as indoors. So for those who haven’t gotten vaccinated yet, especially if you’re younger or think you don’t need it, this is another great reason to go get vaccinated,” Biden said while speaking from the White House on Tuesday.

Since Biden’s Jan. 20 inauguration, the U.S. has put 250 million shots in arms, the president said. Biden also noted that 67 percent of seniors are fully vaccinated, and at least 80 percent of seniors have had at least one shot, which has resulted in significant drops in COVID-19 deaths and hospitalizations among older Americans.  

Health and Human Services Secretary Xavier Becerra also said the guidance should encourage more people to get the shot. 

“The message is clear. You’re vaccinated, guess what? You get to return to a more normal lifestyle. You’re not vaccinated, you’re still a danger,” Becerra said.

More than half the U.S. adult population has received at least one dose of the vaccine, and shots are now available to everyone in the country age 16 and older, but vaccination rates are stagnating. Several states, including Georgia, Mississippi and Montana, are struggling to figure out what to do with excess vaccines.

Both vaccinated and unvaccinated people should continue to wear a mask in most indoor settings, according to the CDC. The U.S. is still recording upward of 50,000 new COVID-19 infections per day, and it’s very hard to identify who is vaccinated and who is not, Walensky said. 

The CDC previously declared that fully vaccinated people could safely take off their masks when gathering indoors in private settings with other fully vaccinated people. Vaccinated people also can safely gather with unvaccinated people from a single household indoors and without a mask on, according to the agency.