Covid restrictions could be brought back next winter to control the virus if needs be.
Professor Chris Whitty made the comments during a press conference at Downing Street just one day after a third lockdown was announced.
The Chief Medical Officer was joined by Sir Patrick Vallance and Prime Minister Boris Johnson to address the nation on Tuesday.
Answering questions from the press, Professor Whitty said that some restrictions may have to be brought back into place next winter to control the virus.
He told the press conference: "If we did not do all the things all of us must now do, if people don't take the stay at home seriously, the risk at this point in time, in the middle of winter with this new variant, is extraordinarily high."
He said the risk level will gradually decrease over time with measures being "lifted by degrees possibly at different rates in different parts of the country, we'll have to see".
He added: "We'll then get over time to a point where people say this level of risk is something society is prepared to tolerate and lift right down to almost no restrictions at all.
"We might have to bring in a few in next winter for example, that's possible, because winter will benefit the virus."
Prof Whitty said that some restrictions may need to be reintroduced next winter, as the virus could thrive in that environment.
He added said: "we all hope the vaccine programme means we don't need anything in the future.
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"But this virus is not going to go away, just like flu, and the time that benefits these diseases most is always winter.
"We have to keep an open mind about future restrictions. It will be nothing on the scale we're doing at the moment.
"But we shouldn't kid ourselves that it will go away with the spring, this isn't a problem that just disappears."
