England’s deputy chief medical officer; Jonathan Van-Tam warned on Wednesday that this year’s Christmas may be difficult to celebrate as the Covid -19 pandemic is not over, urging people to behave with caution and come forward for booster shots.

“Too many people believe that this pandemic is now over. I personally feel there are some hard months to come in the winter and it is not over,” Jonathan Van-Tam told BBC TV, adding that behavior and the uptake of booster shots would determine how tough winter would be.

“Christmas and indeed all of the darker winter months are potentially going to be problematic.”

Prime Minister Boris Johnson lifted restrictions in England in July and has said he plans to cope with Covid over the winter by relying on vaccinations rather than mandating masks or lockdowns.

Johnson has cited Britain’s success in the initial vaccination rollout as he lifted restrictions, but a slower rollout of boosters means that for many vulnerable people, immunity could be waning. Britain reported 293 deaths from Covid -19 on Tuesday, the highest daily figure since March, and there has been an average of around 40,000 new cases each day in recent weeks.

Jonathan Van-Tam also expressed his worry over the increasing numbers of deaths which indicates that “the infection is now starting to penetrate older age groups”.

“Deaths are increasing – there might be some artefacts in the very latest figure – but essentially deaths are increasing,” he told BBC Breakfast and BBC Radio 5 Live.

“If you then look at hospital admissions, those have plateaued in the last four days. And if you look at the total number of patients in hospital with Covid, those have gone down in the last two or three days, but only a small bit.

“So what that tells me is that we have to just wait and see a bit longer – this could be a pause before things go up, it could be the very first signs that things are beginning to stabilize but at a high rate.

“On cases, they are now starting to fall, but that mainly reflects the fact that this big wave we’ve had in teenagers is now starting to slip away. But my worry is that the deaths are increasing and that shows that the infection is now starting to penetrate into those older age groups.

“And that’s why the really key thing is that if you are called for your booster, if you are called for your flu vaccine, please go and get them – this could be really very important this winter, it is not the time to be complacent.”