(CNN) — Britain is facing a “tidal wave” of infections from the new Omicron coronavirus variant, ministers have warned, as they sound the alarm on rapid transmission rates in London and across the country.

On Monday, UK Prime Minister Boris Johnson confirmed the country’s first death of a person with the variant. He told reporters at a vaccination clinic: “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.”

The United Kingdom increased its Covid-19 alert level on Sunday and is once again accelerating its rollout of booster jabs in an effort to respond to the new wave of cases.

Britain is facing a “tidal wave” of infections from the new Omicron coronavirus variant, ministers have warned, as they sound the alarm on rapid transmission rates in London and across the country, and pictured, a covid testing centre sign on November 28, in London, England.

Health Secretary Sajid Javid warned on Monday that the data on Omicron infections is unlike that of earlier variants.

“It’s spreading at a phenomenal rate, something that we’ve never seen before — it’s doubling every two to three days in infections,” Javid told Sky News on Monday. He added that it was too soon to tell if cases of the new variant are milder.

“That means we’re facing a tidal wave of infection, we’re once again in a race between the vaccine and the virus,” he added, echoing language used by Johnson in a televised address on Sunday night.

On Sunday, the Prime Minister set a new target of offering all adults a third shot by the end of December — a month earlier than originally planned. He had previously cut the interval between second and third doses from six months to three. The British government has focused its Covid response around the vaccine program since last summer, and had resisted reimposing restrictions until the Omicron variant came to light.

“I’m afraid it is now clear that two doses of vaccine are simply not enough to give the level of protection we all need,” Johnson said, citing early data that showed the effectiveness of a two-dose regimen is diminished by the new variant, but that boosters still provide a good level of protection.

“No-one should be in any doubt: There is a tidal wave of Omicron coming,” Johnson said. “But the good news is that our scientists are confident that with a third dose — a booster dose — we can all bring our level of protection back up.”

The UK has so far reported 3,137 cases of the Omicron variant, though the true number is likely to be higher. Javid said “about 10 people” are in hospital with the new variant. Overall, the country’s seven-day rolling average of Covid-19 cases has surpassed 50,000 a day.

Omicron was probably behind around 40% of infections in London, Javid said on Monday. But Johnson said that “tomorrow it’ll be the majority of the cases,” underlining how rapid the spread of the new strain has been in its first weeks in Britain.

New guidelines asking people to work from home came into force on Monday. The UK has also brought back its mask mandate for shops and public transport, and now requires proof of vaccination or a negative test for attendees of large events.

The recent flurry of new restrictions marks a sharp turn from the past few months, during which Johnson resisted Europe’s turn towards long-term mitigation measures like vaccine passports and mask mandates.

But the embattled Prime Minister has faced a significant rebellion from his own Conservative backbenchers over his move to reintroduce Covid rules, relying on support from the opposition Labour Party to pass them into law.

Johnson is also embroiled in a scandal over reports that Downing Street held a number of staff parties last winter when the rest of the UK was living under strict rules banning social mixing. He has been forced to deny he fast-tracked Covid rules in order to distract from his political woes.