Boris Johnson has said that at least one patient has been confirmed to have died with the Omicron variant of coronavirus.
Speaking during a visit on Monday to a vaccination clinic near Paddington, west London, the prime minister said: “Sadly, yes, Omicron is producing hospitalisations and, sadly, at least one patient has been confirmed to have died with Omicron.
“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 recognise the sheer pace at which it accelerates through the population. So the best thing we can do is all get our boosters.”
Watch: Sajid Javid says Omicron spreading at 'phenomenal rate'
Earlier on Monday, health secretary Sajid Javid had said there were “about 10” people with Omicron in hospital in England.
He told Sky News: “There is always a lag between infection and then hospitalisation and then, sadly, death.”
Shadow health secretary Wes Streeting said: “The awful news of the UK’s first Omicron death underlines the seriousness of the situation and my heart goes out to their family and friends.
“This is why the booster rollout is so vital and public health measures are necessary to reduce its spread.”
On Sunday, Johnson announced an acceleration of the booster programme, making it open to all adults, as the government aims to give third jabs to one million people a day.
However, the fight against Omicron suffered two serious blows on Monday, when the NHS booking site for boosters crashed and the government ran out of free lateral flow COVID-19 home tests.
Under new rules that come into force from Tuesday, fully vaccinated contacts of someone with coronavirus have been told to take a rapid lateral flow test every day for seven days.
Javid said the rate of the spread of Omicron is "something we've never seen before".
In a prerecorded address to the nation on Sunday evening, Johnson said the UK “must urgently reinforce our wall of vaccine protection” as he set a new deadline of offering everyone over the age of 18 a booster by the new year.
He said scientists had discovered that being fully vaccinated is “simply not enough” to prevent the spread of the coronavirus mutation and that, without a lightning speed mass booster campaign, the NHS could be overwhelmed.
Asked on Monday if the acceleration of the booster programme was “too little, too late”, Johnson replied: “We now want to hit warp speed and we’ll have to attain a pace and a number of daily booster doses that will exceed anything that we’ve done before.”
He said Omicron now represents about 40% of coronavirus cases in London and “tomorrow it’ll be the majority of the cases” in the capital.
“The risk is plainly there, we can see Omicron spiking now in London and some other parts of the country,” he said.
The prime minister refused to rule out further coronavirus restrictions ahead of Christmas.
“Throughout the pandemic, I’ve been at great pains to stress to the public that we have to watch where the pandemic is going and we take whatever steps are necessary to protect public health.”
Watch: Boris Johnson sets out booster plan in face of Omicron 'tidal wave'