The US Centers for Disease Control and Prevention on Thursday announced it was lifting mask-wearing requirements for people fully vaccinated against Covid-19.
"Anyone who is fully vaccinated can participate in indoor and outdoor activities, large or small, without wearing a mask or physical distancing," said CDC director Rochelle Walensky.
"If you are fully vaccinated, you can start doing the things that you had stopped doing because of the pandemic."
The decision follows accumulating data showing the extremely high efficacy of vaccines, not just to prevent symptomatic Covid-19 but also infection.
In the rare case that someone who is fully vaccinated becomes infected, research has shown they are unlikely to have a high viral load in their nose and therefore very unlikely to transmit the disease onward.
According to the CDC's website, masks may still be required on planes, buses, trains, and other forms of public transportation traveling into, within, or out of the United States, and in US transportation hubs such as airports and stations.
Fully vaccinated international travelers arriving in the United States still need to get tested within three days of their flight, or show documentation of recovery from Covid-19 in the past three months.
Walensky said people who are immune compromised should talk to their doctor before giving up their mask.
It has been shown immune compromised people do not respond as well to the vaccines.
Finally, she added, the guidance was subject to change if the situation gets worse.