PRIME Minister Boris Johnson warned that “we’re not out of the woods yet” despite the positive vaccine news from the Oxford-AstraZeneca team.

The news follows positive results from Pfizer and Moderna but none of the jabs has yet been approved for use and getting people inoculated will be a major undertaking.

Addressing the Downing Street press conference, the Prime Minister said: “We can hear the drumming hooves of the cavalry coming over the brow of the hill but they are not here yet.

“Even if all three vaccines are approved, even if the production timetables are met – and vaccines notoriously fall behind in their production timetables – it will be months before we can be sure we have inoculated everyone that needs a vaccine.”

Boris Johnson told a Downing Street press conference that “things will look and feel very different” after Easter, with a vaccine and mass testing.

But he warned the months ahead “will be hard, they will be cold, they include January and February when the NHS is under its greatest pressure”.

That meant the need for new tiers from Wednesday December 2, replacing England’s lockdown, with more areas facing tougher restrictions than the previous regional regime.

The Prime Minister again promised a relaxation of restrictions over Christmas, although details have not yet been finalised with the administrations in Scotland, Wales and Northern Ireland.

Mr Johnson said: “I know that many of us want and need Christmas with our families, we feel this year we deserve it.

“But this is not the moment to let the virus rip for the sake of Christmas parties.

“‘Tis the season to be jolly, but it is also the season to be jolly careful, especially with elderly relatives.”

England’s chief medical officer Professor Chris Whitty expressed an “absolutely massive thank you” to people up and down the country who are volunteering for studies into Covid-19.

“Because as we’ve repeatedly said, it is only science that is going to get us out of this hole,” he said, adding that “it will be a long haul”.

Oxford Vaccine Group director Professor Andrew Pollard said it has been “a very exciting day” and paid tribute to the 20,000 volunteers in the trials around the world, including more than 10,000 in the UK.

“And of course there’s a lot of uncertainty in joining a clinical trial, and I think for all of us, having reached this point today, where we have evidence that the vaccine works, that we have a huge debt of gratitude to all of those people who have taken part,” he said.

Prof Pollard said Oxford’s partnership with AstraZeneca has been “critical” because there was an agreed vision of a “not for profit approach during the pandemic” so that “no one was profiteering from making a vaccine”.

Mr Johnson said there are no plans to close schools a week early to allow a safe period of time before children see elderly or vulnerable relatives at Christmas.

“At the moment we’re not planning to do that,” he said.

“One of the things we really attach, as a country, as a society, a huge importance to is keeping pupils, keeping kids in school and keeping young people in education wherever we can.

“That’s been at the heart of what we’ve been trying to do over the last few months and it’s meant that we’ve had to put a lot of pressure, sadly, on other sectors in order to drive down transmission.”

The Prime Minister described the rollout of any vaccine as a “big logistical challenge”, adding: “That’s why I wanted to enter this important note of caution.

“We haven’t got these things yet, even when we do get them it will take a long time, it will take a while, before we can get the shots in the arms, where they’re needed.”

Professor Chris Whitty added: “It is really critical we realise that the regulators have an absolutely critical next role.

“They independently will look at ‘are these vaccines safe?’ and only when they are satisfied… would it be possible for us to say for sure we can roll these out and then have a plan.”

Boris Johnson told a Downing Street press conference that with a “favourable wind” the majority of people most in need of a vaccination might be able to get one by Easter.

“That would make a very substantial change to where we are at the moment,” he said.

“I don’t want to give any more hostages to fortune than that, but that’s the best information we have.”

Asked about an agreement of rules for Christmas across the nations of the UK, Boris Johnson said: “We want people to be able to celebrate, but we don’t want to ruin it by overdoing it.

“I think there’s a wide measure of agreement about that and I think you can probably expect some news about the way forward pretty soon.”

Mr Johnson stressed that a vaccine would not be compulsory but said people should want to receive one.

He said: “There will be no compulsory vaccination, that’s not the way we do things in this country.

“We think it’s a good idea – I totally reject the propaganda of the anti-vaxxers; they are wrong – vulnerable people, people who need a vaccine should definitely get a vaccine.

“Everybody should get a vaccine as soon as it is available.”

England’s chief medical officer Professor Chris Whitty said: “My advice – any medical practitioner’s advice – would be these should be voluntary vaccinations.

“People should want to take them because they will protect them from a potentially very debilitating – and in some cases, sadly, fatal – disease."

Prof Whitty was asked if there had been any modelling of how many cases and deaths could take place in a worst-case scenario as a result of easing restrictions at Christmas.

He said: “In terms of putting a number on it, to be honest, I wouldn’t put a number on it, because if people do all those things very seriously we will have much less impact from Christmas whilst people are still being able to enjoy it, than if people choose to actually take a very much less public-spirited approach to it and go wild over that period.

“And so I think what we really need to do is we need to say, look if everyone is serious before, during and after then we can minimise the amount of impact it’ll have.

“Of course it will have an impact, and that’s accepted. And this is all part of the balance of having to keep the virus under control but trying to do so in a way that is the least socially and economically damaging.

“It’s a very difficult balance, as we all know, for which there is no perfect answer.

“It’s trying to get the balance as best we can between these competing difficulties.”

Professor Andrew Pollard said trial data hinted the Oxford vaccine could help prevent asymptomatic infections – something that could “stop the virus in its tracks”.

“We have this amazing set-up here in the UK where we have been able to swab over 8,000 people in the trials every week, so we can also pick up the cases of asymptomatic infection,” he told a Downing Street press conference.

“There is a hint in the data that, in one of our groups that had the higher efficacy, we were able to reduce the amount of asymptomatic infection.

“That may mean that there could be fewer people in the population who are spreaders.

“And that starts to stop the virus in its tracks, if we can get there.

“But it’s only a hint at the moment, we need more information.”

Boris Johnson said it was “incredibly interesting and possibly encouraging”.