Boris Johnson has been warned that the UK is a "long way" from emerging from the coronavirus crisis after he signalled ministers would look at easing lockdown measures next month.
The Prime Minister said he wanted England's schools to reopen "as fast as possible" and the Government would be "looking at the potential of relaxing some measures" when restrictions are reviewed on February 15.
But at a Downing Street press conference, Health Secretary Matt Hancock and England's deputy chief medical officer Jenny Harries struck a more cautious tone, highlighting the strain coronavirus cases were putting on the NHS.
The Prime Minister faces pressure from Tories to set out a timetable for pupils to return to class – currently only vulnerable children and those whose parents are key workers are attending school, with home learning for all others.
Mr Johnson could not guarantee that pupils would return before Easter, telling reporters: "We want to see schools back as fast as possible, we want to do that in a way that is consistent with fighting the epidemic and keeping the infection rate down."
The Prime Minister's official spokesman said the Government would examine the data "and that will inform what we may or may not be able to ease from (February) 15 onwards".
But Mr Hancock said that the "facts on the ground" showed the "pressure on the NHS remains huge".
There were 37,000 people in hospital with coronavirus, almost twice the peak in the first wave in April, and more people were on ventilators than at any time in the pandemic.
Mr Hancock said he understood the "yearning" to get out of the lockdown but added: "I think most people understand why it is difficult to put a timeline on it."
While there are "better days that lie ahead", Mr Hancock said, "we have to hold our nerve and persevere through this difficult winter".
Mr Hancock added: "This is not a moment to ease up."
Dr Harries warned: "We are not out of this by a very long way."
The current coronavirus rates were still causing concern, patience was needed about the vaccination programme and the NHS still faced the usual winter pressures, she said.
The Prime Minister visited a vaccination site at Barnet Football Club in north London as the latest figures showed 6,573,570 people in the UK have received a first dose of vaccine – a rise of 220,249 on the previous day's figures.
In the last week, jabs have been administered at a rate of 250 a minute.
Mr Johnson said: "I do think now this massive achievement has been made of rolling out this vaccination programme, I think people want to see us making sure we don't throw that away by having a premature relaxation and then another big surge of infection."
Official figures showed a further 592 people had died within 28 days of testing positive for Covid-19 as of Monday, while there had been a further 22,195 lab-confirmed cases of coronavirus in the UK.
Education Secretary Gavin Williamson is widely expected to confirm this week that there will be no return to the classroom after the February half-term break, as ministers had hoped.
A minister is expected to answer an urgent question on the issue in the Commons on Tuesday.
Robert Halfon, Tory chairman of the Commons Education Committee, told the BBC: "It may be that one thing the Government should consider is that even if there are tighter restrictions in other parts of our society and economy, you have those restrictions in order to enable the schools to open."
Meanwhile, senior ministers are due to meet on Tuesday to consider requiring travellers arriving in the UK to pay to quarantine at a designated hotel, following concerns about new coronavirus variants being imported from elsewhere in the world.
Mr Johnson said: "We have to realise there is at least the theoretical risk of a new variant that is a vaccine-busting variant coming in, we've got to be able to keep that under control."
He said "that idea of looking at hotels is certainly one thing we're actively now working on".
In other developments:
– Less than 60% of people advised to isolate because of coronavirus are doing so, the head of NHS Test and Trace Baroness Harding revealed.
– Labour leader Sir Keir Starmer is self-isolating for the third time since the pandemic started after he came into contact with a positive case.
– Moderna said its vaccine appeared to remain effective against all emerging mutations of coronavirus that have been detected to date.
There was more evidence England's national lockdown is having an impact on the spread of coronavirus.
Case rates are down in every region, with most now at their lowest since before the start of 2021, latest figures show.
London continues to have the highest rate, with 557.8 cases per 100,000 people for the seven days to January 20, but this is down from 770.6 a week earlier, and the lowest since the seven days to December 16.
Yorkshire and the Humber continues to record the lowest rate of any region: 241.2, down from 286.1.