Professor Calum Semple, who sits on the Scientific Advisory Group for Emergencies (Sage), said the UK would be “looking towards the summer” before most of the population is vaccinated.
“And that’s what will give us the immunity, the broad immunity, that allows us to return to normal,” the Liverpool university virus outbreak expert said.
But asked on Ridge on Sunday on Sky News whether that meant social distancing continuing until summer, Semple said: “I doubt that, because if we can vaccinate the frail and the elderly, then that will take the pressure off for groups that will be coming into hospital with severe disease.”
Semple added: “I do think we will be seeing lifting of the restrictions in the spring and I think there’s a lot to be optimistic about here.”
Following the interview, the scientist admitted his comments amounted to “speculation” and his assessment would depend on having “good vaccination” of vulnerable groups and the wider population remaining careful to reduce transmission.
It came after health secretary Matt Hancock said the NHS could start vaccinating people against Covid-19 in December.
The Medicines and Healthcare Products Regulatory Agency (MHRA) has been asked to assess the suitability of the Pfizer/BioNTech vaccine, which has been found to be 90% effective.
The UK has ordered 40m doses of the vaccine, to cover 20m people, with enough for 10m jabs expected to be delivered by the new year.
The government has in total secured deals for 355m doses of prospective vaccines from several separate developers at various trial stages.
Semple’s comments came as Boris Johnson prepared to reveal a tougher three-tiered system of local coronavirus restrictions for England when the national lockdown ends on December 2.
The prime minister will also detail his plan to allow people to see their loved ones at Christmas in a virtual statement to the Commons on Monday.
More areas will be placed into higher tiers to ensure further restrictions are not needed, while the 10pm pub curfew will be relaxed to ensure last orders are called at that time, with venues then forced to close by 11pm.
Chancellor Rishi Sunak on Sunday stressed that Christmas would not be “normal”.
He told Ridge: “I think the good news is we’re going to be exiting national restrictions, which is something that I think people at the beginning of this were doubtful of and we said that was very much what we wanted to deliver, and we are going to deliver that.
“The prime minister will be setting out more details tomorrow about going back to a more localised approach, seeing what we can do to allow families to see each other at Christmas time.
“But it is not going to be normal.”
Johnson is facing a rebellion of 70 Tory MPs who have said they cannot support the return to tiered restrictions unless the government can demonstrate they will slow transmission and “save more lives than they cost”.
The MPs on the Covid Recovery Group also demanded a full cost-benefit analysis of the restrictions on a regional basis “so that MPs can assess responsibly the non-Covid health impact of restrictions, as well as the undoubted impact on livelihoods.”
But Sunak indicated this would not be possible, insisting “it’s very hard to be precise” on the economic impacts of individual restrictions.
Asked if the Government would publish a cost-benefit analysis of future lockdown measures, he told Sky’s Sophy Ridge on Sunday: “It’s very hard to be precise in estimating the particular impact of a one-week restriction.
“What you will see next week when we have the spending review, alongside that will be a set of forecasts from the Office for Budget Responsibility … which will show the enormous strain and stress our economy is experiencing, the job losses that you mention, the forecasts of what will happen, and it’s right that we consider those in the round as we consider the best way to fight the virus.”
This article originally appeared on HuffPost UK and has been updated.