US health officials have eased mask-wearing guidance for people who are fully vaccinated, allowing them to stop using face coverings outdoors in crowds and in most indoor settings.

“Today is a great day for America,” President Joe Biden said during a Rose Garden address heralding the new guidance from the Centres for Disease Control and Prevention (CDC).

“If you are fully vaccinated, you no longer need to wear a mask,” he said, summarising the new guidance and encouraging more Americans to roll up their sleeves. “Get vaccinated — or wear a mask until you do.”

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Vice President Kamala Harris listens as President Joe Biden speaks in the Rose Garden of the White House (Evan Vucci/AP)

The guidance still calls for wearing masks in crowded indoor settings like buses, planes, hospitals, prisons and homeless shelters, but it will help clear the way for reopening workplaces, schools, and other venues — even removing the need for social distancing for those who are fully vaccinated.

“We have all longed for this moment — when we can get back to some sense of normalcy,” said Rochelle Walensky, director of the CDC, at an earlier White House briefing.

The CDC and the Biden administration have faced pressure to ease restrictions on fully vaccinated people — those who are two weeks past their last required Covid-19 dose — in part to highlight the benefits of getting the jab.

The country’s aggressive vaccination campaign has paid off – US virus cases are at their lowest rate since September, deaths are at their lowest point since last April and the test positivity rate is at the lowest point since the pandemic began.

Ms Walensky said the long-awaited change is thanks to the millions of people who have got vaccinated and is based on the latest science about how well those shots are working.

“Anyone who is fully vaccinated can participate in indoor and outdoor activities – large or small – without wearing a mask or physically distancing,” Ms Walensky said. “If you are fully vaccinated, you can start doing the things that you had stopped doing because of the pandemic.”

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Mr Biden said it was a ‘great day’ for America (Evan Vucci/AP)

The new guidance is likely to open the door to confusion, since there is no sure-fire way for businesses or others to distinguish between those who are fully vaccinated and those who are not.

Ms Walensky and Mr Biden said people who are not fully vaccinated should continue to wear masks indoors.

“We’ve gotten this far — please protect yourself until you get to the finish line,” Mr Biden said, noting that most Americans under 65 are not yet fully vaccinated.

He said the government was not going to enforce the mask wearing guidance on those not yet fully vaccinated.

“We’re not going to go out and arrest people,” he added.

“If you haven’t been vaccinated, wear your mask for your own protection and the protection of the people who also have not been vaccinated yet.”

To date about 154 million Americans, more than 46% of the population, have received at least one dose of a Covid-19 vaccine and more than 117 million are fully vaccinated.

The rate of new vaccinations has slowed in recent weeks, but with the authorisation on Wednesday of the Pfizer shot for children ages 12 to 15, a new burst of doses is expected in the coming days.

“All of us, let’s be patient, be patient with one another,” Mr Biden said, acknowledging some Americans might be hesitant about removing their masks after more than a year of living in a pandemic that has killed more than 580,000 in the US and more than 3.3 million people worldwide.