Fully vaccinated people no longer need to wear face masks or stay 6 feet away from others in most environments, whether outdoors or indoors, the Centers for Disease Control and Prevention said in updated public health guidelines released Thursday.

There are a handful of cases where people still have to wear masks – in the healthcare sector or in a business that needs them – even after receiving their final vaccine dose two or more weeks ago, CDC Director Dr. Rochelle Walensky told reporters at a news conference. Fully vaccinated people must continue to wear masks on airplanes, buses, trains and other public transport, she said.

“Anyone who is fully vaccinated can participate in indoor and outdoor activities, large and small, without wearing a mask or physically distancing themselves,” said Walensky. “When you are fully vaccinated you can start doing the things you stopped doing because of the pandemic. We have all longed for that moment when we can return to a sense of normalcy.”

Walensky said people who were not vaccinated should continue to wear masks, adding that they continue to be at risk of mild or serious illness, death, and the risk of spreading the disease to others. People with compromised immune systems should speak to their doctor before giving up their masks, she said.

She added that there is always a chance the CDC will change its guidelines again if the Covid pandemic worsens or additional variants emerge.

“This is an exciting and powerful moment that can only come because of the work of so many people who have made sure that three safe and effective vaccines are given quickly,” she said.

The CDC’s announcement comes just before Memorial Day and July 4th parade season. President Joe Biden has said he hopes that enough Americans will be vaccinated by Independence Day to hold outdoor meetings safely.

Last week, Biden announced his government’s latest goals in the fight against the coronavirus: 70% of adults in the US should receive at least one dose of a Covid-19 vaccine, and 160 million adults should be fully vaccinated by July 4.

As of Wednesday, more than 151 million Americans 18 and older, or 58.7% of the adult US population, had received at least one dose of a Covid vaccine, according to the CDC. Around 116 million American adults, or 45.1% of the American adult population, are fully vaccinated, according to the agency.

To achieve the president’s goal, the government is working to make vaccination with Covid as easy and convenient as possible.

Biden is instructing thousands of local pharmacies to offer walk-in vaccinations to people without an appointment, a senior administration official told reporters last week. The Federal Emergency Management Agency will also support pop-up and mobile clinics aimed at those who may otherwise have difficulty reaching vaccination sites.

On Tuesday, the White House announced a new partnership with Uber and Lyft that will offer free trips to vaccination sites through July 4th.

Thursday’s new CDC guidelines mark a turning point in the pandemic and are likely to encourage more Americans, especially those who are still reluctant to receive the shots, to get the vaccine, health experts say.

U.S. health officials stressed that the Covid vaccines are highly effective, citing several studies, including one from Israel, that found the Pfizer BioNTech shot 97% successful in preventing symptomatic infections in fully vaccinated people.

Dr. Paul Offit, director of the Vaccine Education Center at Philadelphia Children’s Hospital and a member of the FDA advisory board, described the new guidelines as an “important step forward”.

“And another incentive to get vaccinated,” he added.

The instructions are “pragmatic [and] agrees with science, “said Dr. Isaac Bogoch, an infectious disease specialist at the University of Toronto.” It also shows how mass vaccination can really be a path towards normal and that the US is a long way on that path. “

He added that it was “almost impossible” to get this through.

– CNBC’s Rich Mendez contributed to this report.