At least one person has died in Britain after being infected with the Omicron variant, Prime Minister Boris Johnson said on Monday, as the country launched an ambitious Covid booster shot programme to stop the virus' spread.

Britain — among the countries worst hit by the global health crisis since last year — is believed to be the first government to officially announce a death from the virus mutation.

On a visit to a vaccination centre in west London, Johnson said Omicron accounted for about 40 per cent of the cases in the British capital, and hospital admissions were rising.

“Sadly, at least one patient has been confirmed to have died with Omicron,” he told reporters, a day after warning the country was facing a “tidal wave” of infection.

Britain on Sunday sounded the alarm by raising the national Covid Alert Level because of high levels and rising rates of transmission.

In a rare televised address, Johnson said emergency measures were needed to prevent hospitals becoming overwhelmed in the weeks ahead.

All adults will now be able to receive a third dose of a Covid vaccine by the end of December after the government brought forward its deadline by one month.

But in a sign of huge demand, the National Health Service (NHS) vaccination booking site crashed and users requesting rapid testing kits were told they were out of stock.

Long queues were seen at London clinics. At one, Sarah Jackson, 29, said she had taken the morning off to get a jab before visiting her grandparents at Christmas.

“I don't know if it's going to be enough. I was told there is a queue of two hours to register and then two hours to get vaccinated,” she told AFP.

“But I have to go back to work at 1:30pm.”

The “turbocharged” booster programme has seen military planners asked to set up and run extra vaccination centres around the clock.

Some 500,000 booster jabs were given on Saturday but to hit the new deadline that number will have to be doubled every day for the remainder of the year to slow the spread.

Wider measures

Concerns have mounted about a new wave because of indications that two jabs are less effective against infection than three.

There were 1,239 confirmed cases of the variant recorded on Sunday and scientists have said numbers are doubling every two to three days.

Vaccination rates are high in Britain, with more than 81pc or 46.7 million of those aged 12 and over having had a second jab.

Some 23 million or 40pc have so far had a booster.

The new measures come after face masks were made compulsory in indoor public spaces last Friday, and new testing and self-isolation rules for contact cases began on Monday.

Workers were also told to stay at home, leading to a quieter-than-usual Monday morning rush hour. Vaccine passports for certain crowded settings, including at football grounds, are due to be enforced from Wednesday.

The rules apply to England only. The devolved governments in Scotland, Wales and Northern Ireland, which are responsible for health policy, have similar measures.

The race to vaccinate the nation will come at the cost of already delayed elective surgeries, like hip or knee operations, the government admitted.

Johnson's intervention on Sunday sought to refocus attention on the pandemic, after a torrid week in which he and staff were accused of breaking Covid rules last year.

Claims of illegal Christmas parties at Downing Street and across government departments have been seen as undermining public health messaging.

Johnson is also facing a large rebellion from within his Conservative party at a vote in parliament to make the new rules law on Tuesday.

Many Tory MPs are unhappy that freedoms are being restricted again — and even cut further. The vote, though, is likely to pass with opposition Labour support.