A further Covid lockdown may be needed this winter to stop hospitals becoming overwhelmed, a senior Public Health England (PHE) official has predicted.
Dr Susan Hopkins, the PHE strategic response director, warned of a possible rise in cases towards the end of the year.
Meanwhile, a senior member of the Scientific Advisory Group for Emergencies (Sage) said a surge in other respiratory viruses could spell a "pretty miserable winter" ahead.
Prof Calum Semple, an expert in respiratory and outbreak medicine, said there would be a rise in bronchiolitis and community-acquired pneumonia in children and the frail and elderly. However, he predicted a return to "business as normal next year".
It comes after Boris Johnson controversially delayed the lockdown lifting scheduled for June 21 to July 19, despite numerous experts saying the link between Covid cases and deaths has now been broken.
Dr Hopkins said: "We may have to do further lockdowns this winter. I can’t predict the future – it really depends on whether the hospitals start to become overwhelmed at some point.
"But I think we will have alternative ways to manage this, through vaccination, through antivirals, through drugs, through testing that we didn’t have last winter.
"All of those things allow us different approaches rather than restrictions on livelihoods that will move us forward into the next phase of learning to live with this as an endemic that happens as part of the respiratory viruses."
Her comments follow the revelation by The Telegraph that Matt Hancock failed to tell Boris Johnson about a major PHE study showing the effectiveness of the vaccines against the Indian or delta variant during key meetings during which the delay to reopening was discussed.
The analysis showed that the Pfizer-BioNTech vaccine is 96 per cent against hospitalisation after two doses, while the Oxford-AstraZeneca vaccine is 92 per cent effective.
How modelled data underestimated the effect of vaccines
PHE said it is currently too early to say how well the vaccines protect against death in those infected with the Delta variant, but that protection is "expected to be high".
Prof Semple told Times Radio: "I suspect we’ll have a pretty miserable winter because the other respiratory viruses are going to come back and bite us quite hard. But after that, I think we’ll be seeing business as normal next year.
"There’s a sting in the tail after every pandemic, because social distancing will have reduced exposure, particularly of pregnant women and their newborn babies, they will have not been exposed to the usual endemic respiratory viruses.
"The protection that a pregnant woman would give to their unborn child has not occurred. So we are going to see a rise in a disease called bronchiolitis, and a rise in community-acquired pneumonia in children and in the frail elderly, to the other respiratory viruses for which we don’t have vaccines.
"So that’s why we’re predicting a rough July, August and then a rough winter period."
All people aged 18 and over can now book a Covid jab, and thousands of doses we administered at stadiums and football grounds in London over the weekend.
Smaller events are also taking place in local community venues in a drive to vaccinate as many people in the capital as possible, where rates have fallen behind the national average.