While the government has not urged people to cancel plans amid soaring Covid cases, England's chief medical officer has suggested people “prioritise what matters to them” when considering attending parties, reports ITV News Political Correspondent Daniel Hewitt
Britons have been told they should "deprioritise" some social interactions in the run up to Christmas in order to protect meetings with people important to them.
England's Chief Medical Officer Professor Chris Whitty said people eager to spend Christmas with their family should "do only what you need to" to avoid catching Covid and having to self-isolate.
The medical expert said people should "prioritise social interactions that really matter to them", adding "that is going to come increasingly important as we approach Christmas".
"Don't mix with people you don't have to", he added.
But the prime minister told the Downing Street press conference "we're not cancelling people's parties or their ability to mix. What we are saying is think carefully before you go".
Prof Whitty also urged people not to over-interpret reports from South Africa that Omicron causes "milder" disease than other strains, saying it would be "dangerous" to do so.
The professor said it is unhelpful to make direct comparisons with South Africa because recent Covid waves there mean many people have higher levels of immunity.
He said it is a "nailed on prospect" that hospitals will see a "substantial" increase in coronavirus patients after Christmas, adding "all the things that we do know (about Omicron) are bad".
The government is aiming to have offered all adults over-18 a coronavirus booster vaccine before the end of the year and aims to deliver one million jabs a day in order to achieve that target.
Watch the Downing Street press conference in full:
The UK smashed its previous daily booster jab record after administering a huge 656,711 third doses on Tuesday.
But another record was also made as the UK reported its highest ever number of daily, lab-confirmed Covid cases, on Wednesday, demonstrating the fast speed at which Omicron spreads.
A further 78,610 cases were recorded on Wednesday, over 10,000 cases more than the previous record of 68,053 on January 8, 2021.
And a jump of 19,000 cases on Tuesday's total is a record daily increase, demonstrating the extremely fast speed at which Omicron spreads.
Rising Covid cases and the need to self-isolate is leading to closures and staff shortages, reports ITV News Correspondent Lucy Watson
However, Professor Whitty warned these will not be the last and said "records will be broken a lot over the next few weeks as the rates continue to go up".
"What we've got is two epidemics on top of one another - an existing Delta epidemic, roughly flat, and a very rapidly-growing Omicron epidemic on top of it," he told the press conference.
The strain is presenting "probably the most significant threat" of the pandemic so far, according to head of the UK Health Security Agency Dr Jenny Harries, and it could place the NHS in "serious peril".
Sage expert Professor Sir David Spiegelhalter said it is possible that a million people could be isolating with Covid infections on Christmas Day.
The Cambridge University academic told BBC Newsnight: “I haven’t seen the sums behind it, it sounds like it is in fact possible.
“It depends on whether people get tested, because more than half of people who are infected don’t go on and get tested. But we do know there is going to be huge disruption.”
Governments in Westminster, Wales, Scotland and Northern Ireland will discuss their response to the new variant in a Cobra meeting this evening.
Scots have already been urged by First Minister Nicola Sturgeon that they should keep their Christmas Day celebrations as small as possible and told they should only socialise with two other households in the days before and after.
Plan B measures were approved in England on Tuesday, meaning large venues will require all customers to provide proof of their Covid status, either with an NHS vaccine pass or a negative test result, while health workers will need to double jabbed to remain in their jobs.
The PM has so far resisted issuing any further Covid advice, but Health Secretary Sajid Javid was unable to rule out any new restrictions when asked just minutes before this evening's press conference.
Asked if he agreed with Transport Secretary Grant Shapps that there would be no more measures until the new year, the health secretary said: "No-one wants to see any more restrictions.
"These restrictions, whenever they are made, they are really difficult things to do because they have a real impact on people's lives, they can really disrupt their daily activities, what they were perhaps planning to do, and no-one wants to see that.
"At the same time, people want to be safe for themselves, for their families, for their friends. We all know now what we can do. We're learning more about this variant all the time."