Washington (AFP) - The top US health agency on Thursday said it was lifting mask-wearing guidance for people who are fully vaccinated against Covid-19, a watershed moment that President Joe Biden called "a great day" in the long pandemic fight.

The announcement by the Centers for Disease Control and Prevention (CDC) marked an abrupt turnaround after more than a year of urging people to cover their faces to stem the spread.

"Anyone who is fully vaccinated can participate in indoor and outdoor activities, large or small, without wearing a mask or physical distancing," CDC director Rochelle Walensky said during a briefing.

"If you are fully vaccinated, you can start doing the things that you had stopped doing because of the pandemic."

In an emotional address from the White House, Biden declared a major victory in the battle against the virus that has seen more than 580,000 Americans die.

"I think it's a great milestone, a great day," he said.

The move sparked joyful reactions in some, but others experienced whiplash and said they would continue to wear their masks out of caution.

"I'm still going to wear a mask inside," said Mubarak Dahir, a 57-year-old tourist in the capital Washington who was visiting from Florida. "I think it's premature, it's a little dangerous to believe that we are that far already."

But Desmond, a 67-year-old in Lafayette Square, said: "It's great news... we have come a long way in 14 months!"

Accumulating data shows the extremely high efficacy of authorized vaccines, not just to prevent symptomatic Covid-19 but also asymptomatic infection and onward transmission.

Almost 60 percent of US adults now have one or more doses, while cases are falling fast, down to a seven-day-average of 38,000 or 11 per 100,000.

And on Thursday, the campaign to vaccinate adolescents aged 12-to-15 began in earnest following the authorization of the Pfizer vaccine in this age group.

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. Finally, she added, the guidance was subject to change if the situation worsens.

Champions League final moved

The pandemic has killed at least 3,333,603 people worldwide since the virus first emerged in late 2019, according to an AFP compilation of official data. 

Infections are heading down in many parts of the world but still surging in hotspots like Brazil and India, where the death toll has topped 250,000 though experts presume it is higher still. 

Daily new cases have risen 60-fold in neighboring Nepal, a mountainous country of almost 30 million now seeing severe cases flood hospitals as oxygen cylinders empty faster than they can be refilled.

Covid continues to wrack the world of sport, with UEFA announcing Thursday it was moving the Champions League Final between Manchester City and Chelsea later this month from Istanbul to Porto in the hope of allowing English fans to attend.

The UK government placed Turkey on a coronavirus travel red list last week, but a Portuguese government spokeswoman said Portugal is yet to decide on whether or not to allow fans from the UK to travel to the country.

China's early response to the outbreak meanwhile remains contentious, with an independent global panel concluding a "toxic cocktail" of dithering and poor coordination meant warning signs went unheeded.

Australia's Foreign Minister Marise Payne on Thursday praised the panel's work and backed its calls for the World Health Organization to be given greater powers to investigate outbreaks.

"The independent panel is very important...for ensuring that we avoid the experience that the world, this country, our country, so many countries have had to deal with in recent times," she said on a visit to Washington.