US health authorities say those who have received all required Covid-19 jabs can remove their face coverings when outdoors if alone or in small groups of vaccinated people.
New guidelines from the Centers for Disease Control and Prevention (CDC) say masks should still be worn indoors and in crowded settings.
The guidelines are for the fully vaccinated, which means two weeks after a person’s final vaccine jab.
So far, over 95 million Americans have been fully vaccinated.
Following the CDC announcement on Tuesday, President Joe Biden celebrated the new guidance as “extraordinary progress”.
“Our scientists are convinced by the data that the odds of getting or giving the virus to others is very, very low,” Biden said. “The bottom line is clear: if you’re vaccinated you can do more.”
The president also urged Americans who have not yet received their shot to do so, calling it a “patriotic” act.
“Vaccines are about saving your life but also the lives of the people around you. They’re also about helping us get back closer to more normal living.”
CDC director Dr Rochelle Walensky told a White House coronavirus task force briefing that determining whether to wear a mask in larger outdoor gatherings would depend on concerns like how well-ventilated a venue is and how much space is left between people.
Evidence suggests that although Covid-19 viruses can be passed on outdoors, the risks of transmission are extremely low. Early studies indicate that fully vaccinated people are much less likely to spread the virus.
Walensky said mask guidance for the fully vaccinated is intended largely “to protect the unvaccinated”.
“We really do want people who are unvaccinated to limit interactions with people, to go back to the basic principles of increased ventilation, spacing,” she said.
Health officials have noted that the case count in the US is stabilising as the rate of vaccinations continues to grow, and on Tuesday they called for more people to sign up for vaccinations.
According to the CDC, nearly 141 million Americans – about 42% of the total population – have received at least one vaccine dose as of 26 April.