The number of Covid-19 patients in England’s hospitals is approaching the peak seen earlier this year, The UK prime minister said.
Boris Johnson also issued a warning that positive news about a potential Pfizer vaccine was a step in the right direction – but not yet the solution.
He urged people to stick to a newly introduced month-long lockdown and practise social distancing.
About 13,000 people in England are in hospital with Covid-19, he said.
Mr Johnson stressed that when assessing the experimental vaccine, which initial tests show to be 90 per cent effective, it was still “very, very early days”.
Britain has ordered enough doses of the Pfizer vaccine for 20 million people, about a third of the UK population.
“We absolutely cannot rely on this news, as a solution,” Mr Johnson told a press conference on Monday.
Jonathan Van-Tam, the deputy medical officer, said the vaccine news was an important scientific breakthrough but also urged caution.
“So this is like getting to the end of the play-off final. It’s gone to penalties. The first player goes up and scores the goal,” he said.
“You haven’t won the cup yet. But what it does us it tells you that the goalkeeper can be beaten, and that’s where we are today.”
But he was more cautious about its short-term impact.
“Frankly, we’re in the middle of the second wave and I don’t see the vaccines making any difference for the wave we are now in,” Dr Van-Tam said.
“I’m hopeful that it may prevent future waves but this one we have to battle through to the end without a vaccine. We have to keep pressing hard for now.”
Mr Johnson decided to introduce tighter restrictions last week in England as the government struggled to contain a rise in cases.
But he said the plan remained for them to last only until December 2, despite some suggestions the lockdown may be extended.
Scotland, Wales and Northern Ireland have imposed their own restrictions.
About 50,000 people have died of Covid-19 in the UK.