(Reuters) – Fully vaccinated people can safely engage in outdoor activities like walking and hiking without wearing masks but should continue to use face-coverings in public spaces where they are required, U.S. health regulators said on Tuesday.

The updated health advice comes as more than half of all adults in the United States have now received at least one dose of COVID-19 vaccine, according to the U.S. Centers for Disease Control and Prevention (CDC).

“The release of these new guidelines is a first step at helping fully vaccinated Americans resume activities they had stopped doing because of the pandemic, while being mindful of the potential risk of transmitting the virus to others,” the CDC said.

Wearing face masks has been considered by experts as one of the most effective ways of controlling virus transmission. With most COVID-19 transmission occurring indoors, and vaccinations on the rise, the use of masks outdoors has been under public debate for weeks in the United States as Americans look to enjoy the benefits of being fully vaccinated.

New COVID-19 cases have dropped 16% in the last week as the U.S. surpassed 140 million people having received at least one shot of authorized vaccines from Pfizer/BioNTech, Moderna or Johnson & Johnson’s one-dose vaccine.

This was the biggest percentage drop in weekly new cases since February, according to a Reuters analysis of state and county data.

SMALL OUTDOOR GATHERINGS

The agency said fully-vaccinated Americans can safely dine outdoors with friends from multiple households at restaurants and attend small outdoor gatherings with a mixture of fully vaccinated and unvaccinated people.

CDC continues to recommend masking for crowded outdoor events such as parades and sporting events and indoor visits to the hair salon, shopping malls, movie theaters and houses of worship.

The agency classified activities as “red,” “yellow” and “green” based on level of safety for unvaccinated people.

It said unvaccinated people can also walk and run unmasked with household members outdoors safely and attend small outdoor gatherings with fully vaccinated family and friends.

Data on whether vaccinated people can spread infection to those who did not receive their shots is limited and the CDC warned that people should evaluate risk to friends and family before going out without masks.

This is an update to the CDC’s guidance, which in March said people who have been fully vaccinated against COVID-19 can meet without masks indoors in small groups with others who also have been inoculated.

(Reporting by Manojna Maddipatla in Bengaluru; Editing by Caroline Humer and Bill Berkrot)