Clive Dix predicted this would be the case “sometime in August”, in an interview with The Telegraph.
Mr Dix, who became interim head of the Vaccine Taskforce (VTF) last December, said he expected all adults to have been vaccinated at least once by the end of July.
By this time, “we’ll have probably protected the population from all the variants that are known”, he said.
Mr Dix, who stepped down from his role on the VTF last week, added: “We’ll be safe over the coming winter.”
More than 50 million doses of a Covid vaccine have been distributed in the UK, around 16.7 million of which are second doses, according to government figures.
Earlier this week, vaccines minister Nadhim Zahawi said scientists are looking at a range of options for an autumn booster vaccination campaign to protect against a third wave of coronavirus. This could include new jabs to protect against variants or mixing the types of injections given.
But Mr Dix told The Telegraph he felt this could be pushed back into the new year.
“We may decide that we need to boost the immune response, and we’ve got the vaccine to do that. Whether we’ll need to or not, I would think probably not, but we might still do it in case,” he said.
“I really don’t think it should be autumn. We should be thinking about boosting in maybe January or February, because the immune response will be strong.”
His predictions over summer come as UK nations prepare to further ease lockdown restrictions in mid-May, including allowing pubs and restaurants to serve indoors, and socialising to go ahead in homes.
In England, international travel is set to resume from 17 May, with countries on the travel “green list” – those that do not carry the need to quarantine on return – announced earlier this week.
Professor Adam Finn, a member of JCVI, warned last month the easing of restrictions will likely lead a “summer surge” in Covid cases.
Last weekend, Professor Neil Ferguson, from Imperial College London, who advises the government, said his team still had some concerns about late summer and early autumn, although these are “diminishing”.
He said: “If we’re going to see another wave of transmission that’s where it would take place, but the data on the vaccines is getting ever more encouraging, particularly the new data which was released just over a week ago about the fact that vaccines, even if you do get infected if you’ve been vaccinated you’re less infectious.”
Additional reporting by agencies