LONDON — U.K. Prime Minister Boris Johnson confirmed Monday that at least one patient infected with the new omicron variant of Covid-19 has died in the country.

“Sadly yes, omicron is producing hospitalizations and sadly at least one patient has been confirmed to have died with omicron,” Johnson told reporters on a visit to a vaccination clinic near Paddington, London, according to Sky News.

“So I think the idea that this is somehow a milder version of the virus, I think that’s something we need to set on one side and just recognize the sheer pace at which it accelerates through the population. So the best thing we can do is all get our boosters.” he said.

Earlier on Monday, U.K. Health Secretary Sajid Javid told the BBC that 10 people were currently in hospital after being infected with the omicron variant. Javid said omicron was spreading at a “phenomenal rate” and cases were doubling every few days.

It comes after a study announced by the University of Oxford on Monday found that two doses of either the Oxford-AstraZeneca or Pfizer-BioNTech Covid-19 vaccine were substantially less effective at warding off omicron compared to previous variants of the coronavirus.

Scientists were, however, optimistic that booster shots would improve immunity against the new, highly transmissible variant.

In a televised statement on Sunday, U.K. Prime Minister Boris Johnson warned Britain faces a “tidal wave” of omicron infections, and announced that the country would be speeding up its booster program to offer all adults a third dose of a vaccine by the end of the year. The government had previously been aiming to extend its booster scheme to all over-18s by the end of January.

Johnson’s statement came after the chief medical officers of England, Scotland, Wales and Northern Ireland raised the U.K.’s coronavirus threat level to four — the second highest level — in light of the spread of omicron.

The U.K. recorded 48,854 new cases of Covid on Sunday, and cases are rising steadily after dipping briefly in November. For every 100,000 people in the country, 501 are currently infected, according to official data.

Some restrictions, including mask mandates in shops and instructions to work from home where possible, have been reintroduced in England throughout December.

In a report on Friday, the U.K.’s Health Security Agency warned: “If omicron continues to grow at the present rate, omicron is projected to reach parity with delta (equal proportion of cases) in mid-December.”

As of Sunday, 3,137 cases of the omicron variant have been recorded in the U.K., with the government urging the public to book their booster vaccines.

However, high demand has seen many people trying to use the online booking system on Monday put into an online queue, with the U.K.’s National Health Service recommending people try later.

From Tuesday, close contacts of people who have tested positive for omicron will be required to take daily lateral flow tests at home for a week — but on Monday, those trying to order the tests from the government website were told none were available.

While there have been widespread claims that omicron presents with milder symptoms than previous variants, there have also been warnings from the scientific community not to make assumptions.

Epidemiologist Deepti Gurdasani said via Twitter on Monday that there was “no evidence … that omicron is intrinsically ‘milder’ than previous variants,” while White House chief medical advisor Dr. Anthony Fauci said last week that more data was needed to fully assess the risk posed by the variant.

Meanwhile, Pfizer CEO Albert Bourla told the Wall Street Journal last week that the rapid spread of omicron could increase the risk of further mutations.