Professor Chris Whitty also said COVID-19 cases are "rising again", as the UK recorded its highest ever daily tally on Monday.
Sir Prof Chris Whitty has so far not commented on Boris Johnson's decision to end COVID rules a month early.
The government have been accused of providing unclear guidance for the clinically extremely vulnerable.
Joy Morrissey deleted a tweet amid backlash at her comments that Prof Whitty's advice was undemocratic.
The prime minister did not rule out the prospect of new restrictions in response to surging Omicron cases.
The PM is expected to update the country on the latest Omicron numbers.
Professor Tim Spector has urged Brits to stay at home if they have the sniffles and get tested more often.
An expert has warned that high case rates could trigger another lockdown.
As the government insisted it currently doesn't plan to trigger its 'Plan B' of winter COVID restrictions, here are the three key areas which could see rules reintroduced this year.
England's chief medical officer pleaded for people to take up the vaccine after working four weeks on a COVID ward.
'This is a thing we do to protect other people.'
The 58-year-old's account has been suspended for the second time this year.
The money saving expert admitted he was scared to walk down the street after being harassed on the way to playground with young daughter.
'I think we need to be braced for the fact that the coming winter may well be quite a difficult one.'
England's chief medical officer said the government needs to remain alert, particularly towards variants of the virus, for 'probably the next year or two'.
Chris Whitty said people are still vulnerable to catching COVID-19 even if they have had two jabs.
Chris Whitty has warned 'significant numbers' of people will still die from coronavirus later this year – even as millions are vaccinated.
Chris Whitty has hit out at reports that he was resisting Boris Johnson’s plan to reopen schools.
England’s chief medical officer made the welcome claim after a winter crisis which has seen record infections, hospitalisations and deaths.
The 'I'm Too Sexy' singers dismissed outrage over a video calling the England's chief medical officer a liar, saying he is 'lucky to have a job'.
'I don't recall I ever personally said it was by Easter.'
Prof Whitty said the new variant of the virus 'undoubtedly' makes every outdoor situation 'slightly more dangerous'.
England's chief medical officer said there is 'no doubt' normality will return as more vaccinations take place.
England’s chief medical officer said it was their right to refuse to take vaccines.
England's chief medical officer said restrictions will need to be in place for at least the next three months.