Sarah Gilbert, lead researcher on the Oxford Vaccine Development Programme, said chances were “pretty high” of the Oxford/AstraZeneca jab being available by the end of the year.
When asked how many people needed to be vaccinated for life to return to normal, she told the BBC’s Andrew Marr Show: “If we’re trying to protect the most vulnerable, then in this country we’re planning to immunise about 20 million people based on age and also the frontline healthcare workers.
“And that would really have a big effect on hospitals being able to go back to normal. That’s not going to completely prevent transmission, but it should prevent the hospitalisations and severe cases.
“And then to reduce it in the community further we would need more people to be immunised, and it’s going to be something that we get the data on as we start to see the vaccine rollout.”
On the chance of people receiving the Oxford/AstraZeneca jab before the end of the year, she said: “It depends on the age group you’re in and the JCVI (Joint Committee on Vaccination and Immunisation) prioritisations.
“I think the chances are pretty high. But we do need multiple vaccines, all countries need multiple vaccines, the world needs multiple vaccines and we need vaccines made using different technologies, if that’s possible.”
She said this was due to companies potentially encountering problems with the supply of raw materials as doses are produced, which could slow down vaccine rollout if other jabs are not available.
“So having multiple shots on goal, multiple irons in the fire, is what we really need,” she added.
Her words come as hospital bosses warn Boris Johnson that relaxing restrictions could trigger a third wave of coronavirus at the busiest time of year for hospitals.
In a letter to the Prime Minister, NHS Providers urged “extreme caution” in moving any area of England to a lower tier.
The first review of England’s tier allocation is due take place on Wednesday, two weeks after the three-tier system was brought in following the end of lockdown.
But areas should be moved into the highest tier of restrictions “as soon as this is needed, without any delay”, according to the letter from NHS Providers.
Chief executive Chris Hopson told the BBC: “We’re about to hit our busiest time of year so people are really worried that if we relax the restrictions now the NHS simply won’t be able to cope with all of the work that it needs to do in late December, January and February.”
While the letter did not call for a review of the temporary relaxation of measures over Christmas, NHS Providers said it was “vital” the public understands the risks of extra social contact during the festive period.
Social distancing rules will be relaxed for five days between December 23 and 27, allowing family members to hug for the first time in months.
However, on Saturday, public health expert Professor Linda Bauld warned that relaxing coronavirus restrictions over the Christmas period is a "mistake" which will have "consequences", and urged people to see others outside or "in a very modest way".
Prof Bauld said she was concerned about people travelling from areas with high infections to parts of the country with lower prevalence of the virus.
“From a public health perspective, I have to be perfectly honest, I think this is a mistake.
“I think people have to think very carefully whether they can see loved ones outside, or do it in a very modest way.
“I’m also concerned about the travel, people going from high to low-prevalence areas.
“I think it’s going to have consequences.”
A government spokesperson said ministers will not “hesitate to take necessary actions to protect local communities” and that decisions are made based on the latest available data.
“We have introduced strengthened local restrictions to protect the progress gained during national restrictions, reduce pressure on the NHS and ultimately save lives,” the spokeswoman said.
“On top of our record NHS investment, this winter we are providing an extra £3 billion to maintain independent sector and Nightingale hospital surge capacity and a further £450 million to upgrade and expand A&Es.”
On Saturday, the government said a further 519 people had died within 28 days of testing positive for Covid-19 in the UK, with a further 21,502 lab-confirmed cases of coronavirus.
Meanwhile, the health secretary has indicated that towns and villages will not be able to move alert level by being “decoupled” from nearby coronavirus hotspots.
Matt Hancock said in a letter to Tory MPs that “narrow carve-outs” of lower prevalence areas often leads to them “catching up” or “overtaking” areas with higher levels, according to the Daily Telegraph.