The NHS is ready to start providing the new coronavirus vaccine "as fast as safely possible", Health Secretary Matt Hancock has said.
Asked whether it could be available by Christmas, he said that was "absolutely a possibility" - but he expected the mass roll-out "in the first part of next year".
He said vaccination clinics would be open seven days a week, and he was giving GPs an extra £150m.
On Monday, early results from the world's first effective coronavirus vaccine showed it could prevent more than 90% of people from getting Covid. The vaccine has been developed by pharmaceutical companies Pfizer and BioNTech and is one of 11 vaccines that are currently in the final stages of testing.
The UK has already ordered 40 million doses - enough to vaccinate up to 20 million people as each person will need two doses for it to work effectively.
Asked how many people would need to be vaccinated before life can return to normal, Matt Hancock said: "Well the answer to that is we just don't know."
"So the trials can tell you if a vaccine is clinically safe and if it's effective at protecting an individual from the disease. What we can't know, until we've vaccinated a significant proportion of the population, is how much it stops the transmission of the disease."
Mr Hancock told BBC Radio 4's Today programme it would be "a mammoth logistical operation" and highlighted some of the challenges, including getting it from Belgium to the UK while not removing from a temperature of -70C more than four times.
Older care home residents and care home staff are at the top of a list from government scientific advisers of who would get immunised first, followed by health workers. Mr Hancock said NHS staff would go into care homes to vaccinate residents, as well as setting up vaccination venues. Children would not be vaccinated, he said.
However, Prof Sir John Bell from Oxford University said: "I would worry about not giving this to as wide a percentage of the population as we can."
"I'm more of the view that we need to vaccinate further into the population and vaccinate younger people as well, partly because we don't really know what the long term effects of this disease are."
The vaccine will not be released for use until it passes final safety tests and gets the go-ahead from the Medicines and Healthcare products Regulatory Agency.
Source: BBC News, 10 November 2020