President Biden and federal health officials said Tuesday that Americans who are fully vaccinated against the coronavirus no longer need to wear masks outdoors in most situations except for large gatherings - a step, the president said, toward getting “life in America closer to normal” by his target date of the Fourth of July.

“Beginning today, gathering with a group of friends, in a park, going for a picnic,” Mr. Biden said, addressing reporters outside the White House on what he deemed “a beautiful day” in Washington. “As long as you are vaccinated and outdoors, you can do it without wearing a mask.”

Just two days before he marks his 100th day in office, after U.S. coronavirus cases, hospitalizations and deaths declined sharply since January, Mr. Biden remarked that Americans have made “stunning progress.” But his comments were tempered with caution - masks are still necessary at outdoor concerts or sporting events, he said - and he appealed to Americans who have not yet done so to roll up their sleeves and get a shot.

A short while earlier, the Centers for Disease Control and Prevention issued new guidelines saying that Americans who are fully vaccinated against the coronavirus no longer need to wear masks outdoors if they’re walking, running, hiking or biking, either alone or with members of their household, and in small outdoor gatherings.

The risk of the virus spreading outdoors is so low that even unvaccinated individuals do not need to wear a mask if they hike, jog, bike or run alone or with a household member, according to the C.D.C.’s updated advice. People who haven’t gotten their shots can also go without a mask to small gatherings held outside as long as they are with fully vaccinated friends and family.

The guidelines were further relaxed for immunized people: They can take their masks off when they attend small gatherings with people who haven’t gotten their shots, and when they dine at a restaurant outside with people from several households.

The C.D.C. stopped short of telling even fully vaccinated people that they could shed their masks altogether in outdoor settings - citing the worrying risk that remains for transmitting the coronavirus, unknown vaccination levels among people in crowds and the still-high caseloads in some regions of the country. But with the total number of vaccinations rising and the daily number of cases falling, Dr. Rochelle Walensky, the director of the C.D.C. - who warned several weeks ago that she felt a sense of “impending doom” - said she now feels more “hopeful.”

The United States is averaging around 55,000 new cases a day, roughly a 20 percent drop from two weeks ago, according to a New York Times database.

“I know the quarantine and shutdowns throughout the pandemic have been exhausting,” Dr. Walensky said. “I know we all miss the things we used to do before the pandemic and I know we all want to do the things we love and soon. Today is another day we can take a step back.”

Mr. Biden sought to link the news with the administration’s public campaign to get most American adults vaccinated by summer, and tried to offer reassurances that some semblance of normal life could return, concluding his brief remarks with a public service announcement for the vaccine.

In presenting the new guidelines for wearing masks, public health officials on Tuesday emphasized how people who are inoculated could enjoy mask-free leisure activities, rather than how the guidelines also lifted some restrictions for those who had not gotten their shots. It was a concerted message at a time when vaccination rates have dipped, causing concerns about hesitancy in harder-to-reach populations.

But the C.D.C. is maintaining its advice on other safety measures, saying all adults should continue wearing masks and staying six feet apart in large public spaces like outdoor performance or sports events, indoor shopping malls and movie theaters, where the vaccination and health status of others would be unknown. And they still should avoid medium and large gatherings, crowds and poorly ventilated spaces, officials said.

CDC 27 4 2021

The vaccines are highly effective at preventing people from becoming seriously ill from the coronavirus.

“Scientifically the vaccines are good enough that it’s highly unlikely that someone who’s vaccinated is going to be exposed to enough virus outdoors to have a breakthrough infection,” Dr. Marr said.

Early evidence also suggests that vaccinated people may be significantly less likely to transmit the virus, but the exact risks are not yet known.

Masking and distancing are still generally recommended when gathering with unvaccinated people from more than one other household or with an unvaccinated person who is at high risk of severe illness from Covid, or who lives with a vulnerable person.

And there are scenarios in which wearing a mask outdoors can still be an important social signal, said Dr. Mercedes Carnethon, an epidemiologist at Northwestern University. For instance, no vaccine has yet been authorized for children under 16.

nytimes.com, 27-4-2021, Roni Caryn Rabin, Emily Anthes, Sheryl Gay Stolberg