WASHINGTON, May 13 (Reuters) - The US Centers for Disease Control and Prevention (CDC) on Thursday (May 13) advised that fully vaccinated people do not need to wear masks outdoors and can avoid wearing them indoors in most places, updated guidance the agency said will allow life to begin to return to normal.

The CDC also said fully vaccinated people will not need to physically distance in most places. The agency also hopes the guidance will prod more Americans to get vaccinated.

President Joe Biden emerged at the White House for remarks without a mask. "I think it's a great milestone, a great day," he said.

"If you're fully vaccinated and can take your mask off, you've earned the right to do something that Americans are known for all around the world: greeting others with a smile," he said, flashing a brief smile himself.

CDC Director Rochelle Walensky said the new guidance just two weeks after its most recent update, was based on a sharp reduction in cases, expansion of vaccines to younger people and vaccine efficacy against coronavirus variants.

"We followed the science here," Walensky said adding, "a coalescence of more science that has emerged just in the last week."

Biden earlier shed his mask during a meeting with lawmakers, Republican Senator Shelly Moore Capito told reporters. "We heard all about it. The president took his off too," she said.

Some journalists at the White House also shed their masks.

The CDC had faced criticism, even from public health officials, that it has been too cautious in its guidance. Critics have said people need to see more benefit of getting vaccinated in terms of returning to normal activities.

"In the past couple of weeks, we have seen additional data to show these vaccines work in the real world, they stand up to the variants, and vaccinated people are less likely to transmit the virus," the agency said in a news release.

It added, "We needed to take the time to review the full body of evidence to get this right, and that’s how we came to this decision."

The US government last month extended mask requirements across transportation networks through Sep 13. Walensky said the CDC plans to soon issued updated guidance for transit.

The new guidance says vaccinated Americans can resume all travel, do not need to quarantine after international trips and do not need to be tested for COVID-19 if exposed to someone who is COVID-19 positive but asymptomatic.

Masks became a political issues in the United States with then-President Donald Trump resisting mandating masks while President Joe Biden embraced masks and mandated them for transit hubs. Some U.S. states issued aggressive mask mandates while others declined or dropped them months ago.

In late April, the CDC said fully vaccinated people can safely engage in outdoor activities like walking and hiking without wearing masks, but recommended continuing to use face-coverings in public spaces where they are required.