People wanting to celebrate the end of 2020 and welcome the New Year have been told to stick to the rules and avoid gatherings.
NHS England's medical director professor Stephen Powis said that marking the New Year at home with just your nearest and dearest and within the rules would "reduce infections, relieve pressures on hospitals" and help to save lives.
"COVID loves a crowd," he said. "So please leave the parties for later in the year."
Hogmanay celebrations are also off, with First Minister Nicola Sturgeon saying: "I take no pleasure in saying this but we should ring in 2021 in our own homes."
She said there had been "quite a big jump" in cases reported in Scotland on Monday, with 1,895 people testing positive.
"It may be a Christmas lag, but is nevertheless, indicative of a rising trend," she added.
"We'll be glad to see the back of 2020 but for now it is really vital to do everything we can to reduce risk."
For the first time in its history, Scotland's flagship Hogmanay event in Edinburgh is moving online - where it will be headed by actor David Tennant.
Many other nations are also revising their traditional firework spectaculars.
Ms Sturgeon said a muted Hogmanay would help protect the NHS, which is operating under "severe pressure".
While the numbers of people in hospital and intensive care in Scotland is below peak levels in the spring, she said there was not "any room for complacency".
And, at a Downing Street news conference, Prime Minister Boris Johnson echoed Ms Sturgeon's sentiments.
He said: "We are still in the tunnel of this pandemic... but the tunnel has been shortened and we are moving through it.
"So, follow the rules where you live tomorrow night (New Year's Eve) and see in the new year in safety at home.
"That means not meeting up with friends or family unless they are in the same household or support bubble and avoid large gatherings of any kind."
England's deputy chief medical officer Professor Jonathan Van Tam said: "I know New Year is coming up, I know it's normally a time of great festivity and enjoyment.
"But you have just got to play your part now in bringing us back from this very dangerous situation."
He warned of a "grim and depressing picture" as the new coronavirus variant continues to spread across the country.
Police have issued a warning to potential partygoers, telling them to "celebrate the New Year in the comfort of their own homes, not the homes of family and friends" or face "a very significant" fine.
Metropolitan Police commander Paul Brogden said: "The public can expect to see officers deployed across the capital, supporting communities and focusing strongly on the few people intent on breaching and ignoring the guidance put in place to keep everyone safe.
"Officers will also be paying attention to parts of London that are experiencing the highest infection rates."