People in all of England and most of Scotland must now stay at home except for a handful of permitted reasons, as new lockdowns begin in both nations.
Schools have closed to most pupils in England, Scotland and Wales, while Northern Ireland will have an “extended period of remote learning”.
England’s rules will be reviewed on 15 February and Scotland’s this month.
Cabinet Office Minister Michael Gove said: “The more we vaccinate the easier it will be to lift these restrictions.”
Mr Gove confirmed GCSE and A-Level exams in England were being cancelled this year, saying Education Secretary Gavin Williamson will make a statement in the House of Commons on Wednesday on “how we want to make sure children are fairly assessed”.
Chancellor Rishi Sunak has announced that businesses in the retail, hospitality and leisure sectors are to be given a one-off grant worth up to £9,000, with the measure costing £4bn across the UK.
Meanwhile, Prime Minister Boris Johnson is due to hold a press conference in Downing Street at 17:00 GMT with chief medical officer for England Prof Chris Whitty and the government’s chief scientific adviser, Sir Patrick Vallance.
In Wales, which has been in a national lockdown since 20 December, schools and colleges will stay shut until 18 January for most pupils.
Northern Ireland, which entered a six-week lockdown on 26 December plans to put its stay-at-home message into law, and will have an “extended period of remote learning”, the Stormont Executive said.
It comes after the UK reported a record 58,784 cases on Monday, as well as a further 407 deaths within 28 days of a positive test.