Professor Jonathan Van-Tam has warned of a "potentially problematic" Christmas due to COVID-19 and said he thinks there will be "hard months to come".
England's deputy chief medical officer said the UK is at "half-time in extra time" in tackling coronavirus.
"I think the final whistle in terms of - I can't predict it - but my personal view is that we've got a few more months to run, and I think we'll be in a much calmer set of waters by spring," he told BBC Breakfast.
Christmas 'could be problematic' - latest COVID updates
rof Van-Tam said too many people believe the pandemic is now over.
"I personally feel there are some hard months to come in the winter and it is not over," he said.
Asked how a Christmas lockdown can be prevented, he said: "Christmas, and indeed all of the darker winter months, are potentially going to be problematic."
He said the things that "are really going to determine this" are the success of the vaccination programmes and how careful people are, particularly in the next couple of months.
"I think a whole range of behaviours, including the use of face coverings, but generally the caution that people take or don't take in terms of interacting with each other - that is going to be a big determinant in what happens between now and the kind of darkest months of the winter," he said.
He said it was crucial for people to take up offers of booster and flu jabs.
Prof Van-Tam said infection rates are still very high at the moment - higher than in most of Europe.
"It's of concern to scientists that we are running this hot this early in the autumn season," he added.
While he acknowledged that hospital admissions have levelled off in the last four days, he said he was worried deaths were rising and there were signs infections were starting to "penetrate" older age groups.
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Asked about Sir Jeremy Farrar's resignation from the Scientific Advisory Group for Emergencies (SAGE), he said: "I think it's very clear he felt that a lot of the information that the government need to have from scientists has now been given, and he recognised the need that he had to really re-focus on his work at the Wellcome Trust."
On the subject of masks, Prof Van-Tam said they are beneficial "but they are probably most useful when used in combination with other things".
He said he did not think people should wear face coverings while seated in indoor settings that involve food or drink, but recommended them for entering, leaving and moving around venues.
He said in cinemas and theatres "you're not interacting with anyone in there other than the audience or the actors on the screen, you're not interacting with the audience, you are seated quite close together, and for most people there should be relatively little personal expense involved in wearing a face covering in those kinds of settings."
He said it would be "very socially inhibiting" to wear masks in clubs, adding: "I think if the epidemiology gets worse in the UK that on its own would not be enough in those kinds of venues."
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