The U.S. Centers for Disease Control and Prevention (CDC) issued new mask guidance for fully vaccinated Americans on Tuesday, saying they can go outside without a mask unless they are in a big crowd of strangers. This revised guidance comes as nearly 142 million Americans have received at least one dose of a coronavirus vaccine as the nation continues to race towards potential herd immunity.

"Over the past year, we have spent a lot of time telling Americans what they cannot do, what they should not do," CDC Director Dr. Rochelle Walensky stated during a press briefing on Tuesday. "Today, I'm going to tell you some of the things you can do if you are fully vaccinated."

Under the CDC's updated guidance, individuals fully vaccinated or not can meet with fully vaccinated people indoors without wearing a mask or social distancing, and engage in outdoor activities like exercising or meeting with a small gathering of other fully vaccinated people without a mask.

The CDC defines fully vaccinated people as those two weeks after receiving their second dose of either the vaccine developed by Pfizer (PFE  )-BioNTech (BNTX  ) or two weeks after their dose of the one-shot Johnson & Johnson (JNJ  ) vaccine.

For unvaccinated people, the CDC recommends that they continue to wear masks at small outdoor gatherings that include other unvaccinated people. They also should wear facial covers when dining outside with friends from multiple households, the CDC says.

And for everyone, fully vaccinated or not, the CDC recommends that they continue to wear masks at crowded outdoor events like concerts or sporting events. The CDC also suggests that people wear masks when getting their haircut, visiting an indoor shopping center, riding public transit, going to an indoor movie theater, restaurant or bar, attending a worship service, or exercising at a gym, regardless of vaccine status.

"In public spaces, the vaccination status of other people or whether they are at increased risk for severe COVID-19 is likely unknown," the CDC noted in its guidance. "Therefore, fully vaccinated people should continue to follow guidance to protect themselves and others, including wearing a well-fitted mask, when indoors or in an outdoor setting or venue where masks are required."

Currently, about 29% of the United States population is fully vaccinated against COVID-19, according to CDC data, with about 43% receiving at least one dose.