The UK has recorded the highest daily total of lab-confirmed coronavirus cases since the pandemic began, as the Omicron variant spreads.
Official figures show there had been 78,610 new cases recorded as of 9am today.
British Prime Minister Boris Johnson told a press conference that hospitalisations had risen 10% nationally and by almost a third in London in the past week.
However, fewer people in the older, vulnerable category were being admitted to hospital with coronavirus.
England's Chief Medical Officer, Professor Chris Whitty, warned that there was still no clear data on key questions about Omicron, including hospitalisation rates.
He said there should be "really serious caution" over reports that a reduction in hospitalisations was being seen in cases of Omicron in South Africa.
He told the press conference: "The first caution on this is simply a numerical one - if the rate of hospitalisation were to halve but you're doubling every two days, in two days you're back to where you were before you actually had the hospitalisation.
"If the peak of this is twice as great, then halving of the size of the hospitalisation rate, you still end up in the same place. And this peak is going very fast."
Prof Whitty added: "The second point I wanted to make, which I'm not sure it's fully been absorbed by everybody, is that the amount of immunity in South Africa for this wave - because of a prior Delta wave and vaccination - is far higher than it was for their last wave.
"And therefore the fact that there is a lower hospitalisation rate is unsurprising. That doesn't mean that there isn't some degree of slightly milder disease, that is possible.
"But I just think there's a danger people have over-interpreted this to say, this is not a problem and what are we worrying about? I want to be clear, I'm afraid this [Omicron] is going to be a problem."
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Prof Whitty said there were "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 said: "I'm afraid we have to be realistic that records will be broken a lot over the next few weeks as the rates continue to go up."
Boris Johnson confirmed that the 15 minute wait time following vaccination will end, to help speed up the booster programme.
Jabs are being rolled out "everywhere", he told the press conference, adding: "We have boosted more than 45% of all adults in England."
Mr Johnson said the UK has "twice as many boosters than the EU and more than twice as many as the US".
The rebellion was the second biggest by Conservative MPs since they voted against his predecessor Theresa May's Brexit deal in 2019.
Even though the measures to combat the spread of the Omicron variant passed, the scale of the resistance surprised many and gave a clear message about Mr Johnson's leadership and authority.
In parliament, main opposition Labour leader Keir Starmer said Mr Johnson was "the worst possible prime minister at the worst possible time" and "too weak to lead".
"His own MPs have had enough. They won't defend him. They won't turn up to support him. They won't vote for basic public health measures," he said.
Mr Johnson, who has warned of a "tidal wave" of Omicron that could overwhelm health services, said he understood the "legitimate anxieties" of colleagues.
But he added: "I believe the approach we are taking is balanced and proportionate and right for this country."
Mr Johnson will be well aware of the implications for such a haemorrhaging of support: Tory MPs forced an internal vote of no confidence in May and she had to quit.
Conservative MPs indicated that they were not yet at that stage.
But Mark Harper, May's former enforcer in parliament, told Times Radio it was "a very clear message that colleagues are not happy" with the government at the moment.
Conservative MP Geoffrey-Clifton-Brown said Mr Johnson, who secured the Tories an 80-seat majority at the last general election, needed to listen.
If he failed to do so, he could face a leadership challenge in the new year, he added.
Meanwhile new analysis suggests the Omicron variant is now the dominant Covid-19 strain in London.
Some 51.8% of a sample of new coronavirus cases in London with specimen dates for 11 December and 12 December were found to have S gene target failure (SGTF) - a way of detecting the likely presence of Omicron.
Additional reporting PA
