Britain announced Sunday that it has given more than 20 million people at least one dose of a coronavirus vaccine, with the rapid rollout providing hope in a country with Europe's highest death toll.

Prime Minister Boris Johnson called it "a huge national achievement" while praising National Health Service staff and others involved for "tireless work". Health Secretary Matt Hancock made the announcement in a video message on Twitter, saying: "I'm absolutely delighted that over 20 million people have now been vaccinated."

A total of 20,089,551 people have received a first dose, according to government figures released Sunday. But dampening the good news was the detection of a coronavirus strain that emerged in Brazil, which is feared to be more contagious and more resistant to vaccines.

In mid-February, the UK met a government target of 15 million of the most vulnerable people receiving first doses. The government says it plans to offer a first jab to the whole adult population by the end of July.

Only Israel and the United Arab Emirates have vaccinated more people per head of population. Smiling, Hancock said "I want to thank every single person who has come forward to get the jab," calling this "the route out of this for all of us."

"There's a long way to go but we're making big strides," he said.

The UK's vaccination programme has rolled out fast since its start in early December, when it became the first country in the world to begin mass inoculation with a fully trialled vaccine.

Earlier failures in contact tracing and controlling the spread of infection saw cases soar in the UK and the country's death toll of 122,705 is the highest in Europe.

The country is still under national lockdown but daily cases, hospitalisations and deaths have all fallen dramatically since late January, despite the emergence of a more infectious variant in the country. Another variant that emerged in Manaus, northern Brazil, has been detected in six people in the UK, one of whom could not be located due to incomplete contact information, health authorities said on Sunday.

There were 6,035 new daily cases reported Sunday and 144 deaths, the lowest figures since early autumn. On Thursday, Britain lowered the country's virus alert level down one notch from the highest possible, saying the fall in cases had reduced the threat to the state-run National Health Service.