The jab was given the green light by the Medicines and Healthcare products Regulatory Agency (MHRA) on Wednesday and will be rolled out from 4 January.
It is the second COVID-19 vaccine to be approved in the UK, following the rollout of a rival jab by Pfizer and BioNTech.
Andrew Hayward, a member of the government’s New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), said the Oxford vaccine is crucial in reducing the impact of coronavirus.
Watch: What do we know about the Oxford vaccine?
He told BBC Breakfast: “It is a game changer. It’s exactly what we need right now.”
The UK has ordered 100 million doses of the newly approved vaccine, enough for 50 million people.
Why is the Oxford vaccine a ‘game changer’?
Hayward, professor of infectious diseases epidemiology at University College London, described the vaccine as a “game changer” because it doesn’t need to be stored at very cold temperatures like the Pfizer jab.
This means the vaccine can be taken to where it’s needed, rather people having to be brought to limited places where it can be delivered.
As a result, Prof Hayward said, “All of the centres that would normally get involved in vaccination, all the GP practices, as well as more simple community centres, for example, can get involved in the vaccine.”
He added: “So it should make for a step change and it should also allow us to reach out to the most affected communities.”
When will the rollout start?
Health secretary Matt Hancock confirmed that rollout of the Oxford vaccine will begin on 4 January and will be accelerated in the first few weeks of next year.
He said the speed of delivery will depend on how fast the vaccine can be manufactured but that the NHS aims to eventually deliver 2 million vaccinations a week.
AstraZeneca said it aimed to supply millions of doses in the first quarter of next year as part of an agreement with the government to supply up to 100 million doses in total.
Chief executive Pascal Soriot said the company will ramp up production of the vaccine “very rapidly” and will be able to deliver up to 2 million doses a week.
Soriot told BBC Radio 4’s Today programme: “In January we will already possibly be vaccinating several million people and by the end of the first quarter we are going to be in the tens of millions already.”
Whether they receive the Oxford/AstraZeneca jab or the one from Pfizer/BioNTech, people will be given their first dose of the vaccine followed by a second dose up to 12 weeks later.
The aim is to give as many people as possible a first dose of a COVID-19 vaccine to maximise the number who get some protection against the virus.
Welsh health minister Vaughan Gething said the impact of the vaccine would not be seen “for some months” as it would take time to reach everyone.
He warned the jab would not be “an instant fix” and the pressure on the NHS would continue this winter so it was important people adhered to social distancing regulations.
Gething said: “We won’t receive all the doses at once and we have to be realistic about the scale and pace of delivery when we are vaccinating the entire adult population.”
How long does protection last?
Prof Hayward said the Oxford/AstraZeneca vaccine may need to be updated as the virus evolves.
He told BBC Breakfast: “Some of the unknown questions in this as yet are exactly how long the protection will last?
“We know that it will last at least six months but beyond that we would expect it to last, but it’s likely that we’ll need repeated doses over time and we may need to update the vaccine over time as the virus evolves.”
But he said new technologies made it possible to make changes on a more rapid time frame than previously.
Can vaccines handle mutations?
Oxford’s Professor Andrew Pollard said it should be “entirely possible” to tweak vaccines to deal with new variants of the virus, if necessary.
Prof Pollard told the Today programme: “At the moment there’s no evidence that the vaccines won’t work against a new variant but that is something which we have to look at.
“We can’t be complacent about this variant, or perhaps future variants.
“And so one of the really important things that science has to continue to do now as we move forwards is to monitor the viruses that are around, and to make sure that vaccines still are effective against them.
“If in the future, it was necessary to tweak the vaccines that’s entirely possible to do, but I don’t think that’s something to be concerned about today, but we can’t be complacent, we have to keep watching.”
Watch: Creation of Oxford vaccine was ‘astonishing effort’