Live updates: follow the latest news on Covid-19 variant Omicron
Prime Minister Boris Johnson, in a recorded address to the nation on Sunday evening, said Britain “must urgently reinforce our wall of vaccine protection” as he set a new deadline of inoculating everyone over 18 by the new year.
Mr Johnson said scientists had discovered that being fully vaccinated was “simply not enough” to prevent the spread of the coronavirus mutation and that, without a rapid mass booster campaign, the National Health Service could be overwhelmed.
Amid growing fears of another lockdown if the booster programme fails to effectively tackle Omicron, Mr Johnson said people should rush to get booster vaccines to protect "our freedoms and our way of life".
After his announcement, the pound fell 0.4 per cent to $1.3225, while it was broadly steady against the euro at 85.29 pence.
The mission to administer millions of shots by December 31 will involve 42 military planning teams sent across every health region, extra vaccine sites and mobile units, extended clinic opening hours to allow people to be vaccinated around the clock and at weekends, and the training of thousands more volunteer vaccinators.
The UK Covid alert level was raised to Level 4, up from Level 3, after a rapid increase in the number of Omicron cases.
The UK, as of Sunday, recorded another 1,239 cases of the strain, bringing the total to 3,137 – a 65 per cent increase week on week – although Education Secretary Nadhim Zahawi said the actual number was likely to be 10 times as high.
Health Secretary Sajid Javid said on Monday that in England, no Omicron-related deaths had yet been confirmed and only 10 people had been admitted to hospital with the variant. But he said Omicron was probably behind about 40 per cent of infections in London.
In his address, Mr Johnson said: “We’ve already seen hospitalisations doubling in a week in South Africa and we have patients with Omicron here in the UK right now.
“At this point, our scientists cannot say that Omicron is less severe.
“And even if that proved to be true, we already know it is so much more transmissible that a wave of Omicron through a population that was not boosted would risk a level of hospitalisation that could overwhelm our NHS and lead sadly to very many deaths.
“So we must act now. Today we are launching the Omicron emergency booster national mission, unlike anything we’ve done before in the vaccination programme, to get boosted now.
“A fortnight ago I said we would offer every eligible adult a booster by the end of January. Today, in light of this Omicron emergency, I’m bringing that target forward by a whole month.
“Everyone eligible aged 18 and over in England will have the chance to get their booster before the new year.”
Mr Johnson said the UK government would support the devolved administrations to “accelerate” their own introductions of third shots.
He said the decision to speed up the inoculation rate would mean some NHS appointments would be postponed until the new year and there would be “even greater” cancellations if the Omicron wave was allowed to rise.
Every adult over 18 in England who has had a second dose of a vaccine at least three months ago will be able to have their booster from Monday, he said.
Mr Javid said ministers had set themselves a “phenomenal target” with the booster campaign to tackle Omicron. “We are throwing everything at it,” he said.
The health secretary said scientific research has shown that two doses of a vaccine is "not enough" to protect a person against Omicron but a third dose would offer "excellent protection" against symptomatic infection from the variant.
In an interview on Sky News, he made a direct appeal to the public to come forward when they are called for their third shot of a vaccine.
“Please play your part, this could not be more important,” he said. “We need to win this race against the growth of this virus, we’ve never seen this kind of growth before.
“So please do come forward, protect yourselves, your loved ones and your community.”
Mr Javid said it is “unfair” to argue that the surge in Omicron cases in the UK could be caused by the AstraZeneca vaccine not being strong enough to stave off Covid-19. He said regardless of whether a person has received the AstraZeneca, Moderna or Pfizer vaccine, everyone would need a booster shot to protect against Omicron.
Chris Hopson, chief executive of NHS Providers, said the current level of pressure being put on health services was “not sustainable”.
He said a combination of record highs in 999 calls, the second-highest number of emergency department admissions, elective procedure backlogs, the extension of the booster campaign and social care pressure means the NHS was “busier than it’s ever been before”.
He said that even "before the traditional winter peak in January", hospitals were already "beyond full stretch", but as you’d expect everybody on the NHS front line is doing absolutely the best they can to provide the best possible care”.
He said the prime minister had demanded an “extraordinary effort” from the NHS at a time when staff are “very, very tired”.
“I think staff are worried, to be frank, that this level of pressure is going to become normalised and it’s not sustainable."
NHS England said people may see their planned appointments cancelled while the health service races to meet the government’s booster target.
GP teams will be asked to “clinically prioritise their services to free up maximal capacity” to support the programme, alongside delivering critical appointments such as cancer, urgent and emergency care.
Matthew Taylor, chief executive of the NHS Confederation, which represents hospitals and health providers, said it would be “very tough” for staff to double the current rate of vaccines given the fact they are already under “immense pressure”.
He pointed out that the government’s “enormously ambitious plan” comes only weeks after Mr Javid unveiled a strategy to name and shame GP surgeries that have a low rate of in-person appointments.
“It’s only a few weeks since politicians were indulging in attacking members of the primary care team for the fact that they weren’t always able to offer face-to-face appointments,” Mr Taylor told BBC Radio 4's Today programme.
“It’s really important that the government is clear with the public about the consequences it is going to have for the rest of what the health service can offer.”
A new study carried out in the US suggested a person could get more protection from a booster shot if it was administered in the afternoon.
The research from Massachusetts General Hospital showed the time of day a vaccine is administered can affect the number of antibodies produced due to a bodily function.
The 24-hour cycle, known as a circadian rhythm, can have an effect on how seriously some people suffer from diseases and how effective some treatments are.