Boris Johnson has announced plans to offer booster vaccines to everyone over the age of 18 by the end of January.
Speaking at a Downing Street press conference on Tuesday afternoon the PM set the target of everyone eligible for a booster to be offered one by that date.
Mr Johnson said at least 400 military personnel will help the NHS and “the fantastic jabs army of volunteers” deliver jabs, with centres "popping up like Christmas trees".
The PM addressed the country as the number of cases of the variant identified so far across the UK rose to 22.
He said he would be “throwing everything” at the variant, which has concerned scientists around the world.
Mr Johnson said: “We've already done almost 18 million boosters across the UK but we've got millions more to do to protect the most vulnerable.
"Then we'll move down the cohorts rapidly, and working together with the devolved administrations we want to ramp up capacity across the whole United Kingdom to the levels we achieved in the previous vaccination effort.
"We're going to be throwing everything at it in order to ensure that everyone eligible is offered that booster, as I say, in just over two months."
Mr Johnson said vaccines will be given at 1,500 community pharmacy sites and extra hospital hubs in England.
He said as with first jabs, the vaccine programme will be working through people by age group going down in five-year bands “because it is vital that the older and the more clinically vulnerable get that added protection first.”
"So, even if you have had your second jab over three months ago and you are now eligible, please don't try and book until the NHS says it is your turn,” he added.
The PM said: "I know the frustration that we all feel with this Omicron variant, the sense of exhaustion that we could be going through all this all over again.
"But today I want to stress this, today that's the wrong thing to feel because today our position is and always will be immeasurably better than it was a year ago.
"What we're doing is taking some proportionate precautionary measures while our scientists crack the Omicron code.
"And while we get the added protection of those boosters into the arms of those who need them most."
Asked whether people should cancel Christmas parties and nativity plays, Mr Johnson said: “We don’t want people to cancel such events and we think that overwhelmingly the best thing for kids is to be in schools.”
Health Secretary Sajid Javid said the booster programme would be put "on steroids" to meet the target.
He said boosting the nation’s immunity is the best line of defence against the threat of the variant, and the most important way we can return to normality quicker.
The Health Secretary said: “What we’re seeing recently has brought back memories of the strain of the last winter.
“But although we can’t say with certainty what lies ahead, we have one huge advantage that we didn’t have back then: our vaccination programme, which has already done so much to keep this virus at bay.”
And the booster programme expansion comes after the Joint Committee on Vaccination and Immunisation (JCVI) advised that all adults aged 18 to 39 should be offered a booster dose of the Covid-19 vaccine, in order of descending age groups, to increase their level of protection.
They also slashed the gap needed between a second and third dose from six months to just three.
Those aged 40 and over are already eligible for a booster vaccine.
The JCVI has said that 12 to 15-year-olds should be offered a second jab - to be given at least 12 weeks after the first.
NHS England chief executive Amanda Pritchard said she was aiming to free up capacity to allow hospitals, GPs and other services to administer more booster jabs.
Ms Pritchard said GPs and pharmacies would be offered £15 per shot until the end of January, with an additional £5 for those administered on a Sunday and a £30 premium for those delivered to the housebound until the end of next month.
She told the press conference: "We will need to expand vaccination capacity right across the NHS.
"Hundreds of hospitals are already jabbing their own staff. We're now asking them to vaccinate other local NHS workers, eligible patients and social care staff as well.
"Around 30 hospitals are already offering jabs to the public through the national booking service and dozens more will be coming online through early next week.
"Our hard-working GPs, community pharmacists and primary care colleagues have delivered the lion's share of the vaccinations so far. We're looking at how we can help them to do even more by cutting other burdens on them to free up clinicians' time."
Meanwhile, health experts said the winter period was “a time for caution” and urged people to do “anything that they can do to reduce the risk” of catching Covid.
Professor Adam Finn, a member of the Joint Committee on Vaccination and Immunisation (JCVI), said: “It goes on making sense that people should recognise that this virus has not gone away, and anything that they can do to reduce the risk to themselves, their families, and the people they’re in contact with makes good sense.
“So I’m very pleased that people are now being encouraged to wear masks when indoors at the moment, lateral flow tests are a very good way of finding out whether or not you’ve got the infection, so people should carry on doing those.”
Scientists fear the new variant could be both more transmissible and vaccine resistant - prompting the Government to introduce fresh curbs to stem the spread of infection.
Health Secretary Mr Javid has urged Britons to plan for a normal Christmas as health authorities seek conclusive data on the extent of the threat posed by the strain.
All travellers returning to the UK must take a PCR test and self-isolate until they receive a negative result, while contacts of suspected Omicron cases must self-isolate, regardless of their age or vaccination status.