Britain's Medicines and Healthcare products Regulatory Agency (MHRA) has authorized emergency use of the vaccine developed by AstraZeneca and Oxford University, the government and AstraZeneca announced on Wednesday.
In a statement published by the US pharmaceutical company, the authorisation recommends two doses administered with an interval of between four and 12 weeks.
AstraZenenca said this regime was shown to be "safe and effective at preventing symptomatic COVID-19" during trials, with no severe cases and no hospitalisations more than 14 days after the second dose.
British Health Secretary Matt Hancock said the vaccine will start being delivered on Wednesday so that people can receive the jab from 4 January.
"I am now, with this approval this morning, highly confident that we can get enough vulnerable people vaccinated by the spring that we can now see the route out of this pandemic," he told Sky News.
"It is going to be a difficult few weeks ahead. We can see the pressures right now on the NHS, and it is absolutely critical that people follow the rules and do everything they can to stop the spread, particularly of the new variant of this virus that transmits so much faster.
"But we also know that there is a route out of this. The vaccine provides that route out. We have all just got to hold our nerve over the weeks to come."
Further measures
Hancock added that further measures to curb the spread of Covid-19 will be announced in Parliament later on Wednesday following a rise in the number of cases.
People who are at the "highest risk" of contracting Covid-19 will receive the vaccine first, in accordance with advice from Britain's Joint Committee on Vaccination and Immunisation.
A government statement published on Wednesday said: "Now the NHS will begin putting their extensive preparations into action to roll out the Oxford University/AstraZeneca vaccine.
"With two vaccines now approved, we will be able to vaccinate a greater number of people who are at highest risk, protecting them from the disease and reducing mortality and hospitalisation."
Prime Minister Boris Johnson tweeted: "It is truly fantastic news – and a triumph for British science – that the [AstraZeneca/Oxford] vaccine has been approved for use.
"We will now move to vaccinate as many people as quickly as possible."
Second vaccine approved
The vaccine is the second to be approved for usage in Britain.
The Pfizer/BioNTech vaccine was the first jab given the green light in Britain by the MHRA on 2 December and began being rolled out to vulnerable and elderly people the following week.
Doctors from England, Scotland and Wales previously said that they were waiting for the approval of the AstraZenenca and Oxford vaccine before they could start rolling out jabs to their patients.
This is due to the fact that the Pfizer/BioNTech vaccine requires specific storage of being kept at minus-70 degrees Celsius to maintain optimal efficacy. It also has to be mixed with another liquid before it can be administered.
The AstraZeneca/Oxford vaccine meanwhile has been created differently, with more similarities to a traditional vaccine, so it will be sent to vaccination centres in refrigerated vans or cool boxes and stored in a special vaccine fridge between 2 to 8 degrees Celsius that also protects it from light.
The British government has ordered 100 million doses of the Oxford University vaccine, which is enough to vaccinate 50 million people.
AstraZeneca said it plans to supply "millions" of doses in the first quarter.
