The UK has become the first country in the world to approve the Covid-19 vaccine from Pfizer and BioNTech, paving the way for vaccination to start next week.
The jab has been shown in studies to be 95% effective and works in all age groups.
The UK has ordered 40 million doses of the vaccine, enough to vaccinate 20m people.
Around 10m doses will be available for use in the UK shortly for priority groups, including healthcare workers.
A list of who will receive the vaccine first will be set out later on Wednesday.
A Department of Health and Social Care spokesman said the Medicines and Healthcare products Regulatory Agency (MHRA) had approved the jab after “months of rigorous clinical trials and a thorough analysis of the data by experts” from the regulator.
He said they have concluded that the vaccine has “met its strict standards of safety, quality and effectiveness”.
Health Secretary Matt Hancock told Sky News the UK was the first country in the world to have a “clinically authorised vaccine”.
He added: “This is fantastic news.
“The MHRA, the fiercely independent regulator, has clinically authorised the vaccine for rollout.
“The NHS stands ready to make that happen.
“So, from early next week we will start the programme of vaccinating people against Covid-19 here in this country.”
Mr Hancock said there would be “three modes of delivery” of the vaccine, with hospitals, mass vaccination centres and GPs and pharmacists offering the jab to those most in need.
He said: “Fifty hospitals across the country are already set up and waiting to receive the vaccine as soon as it’s approved, so that can now happen.”
On the challenge posed by the need for the vaccine to be stored at an ultra-low temperature of around -70C, he added: “This is a challenging rollout and the NHS in all parts of the UK stands ready to make that happen.
“They are used to handling vaccines and medicines like this, with these sorts of conditions.
“It’s not easy but we’ve got those plans in place.”
Nadhim Zahawi, the newly-appointed minister responsible for overseeing the vaccination rollout, tweeted: “Major step forward in the fight against Covid-19 today.”
Business Secretary Alok Sharma tweeted: “The UK was the first country to sign a deal with Pfizer/BioNTech, now we will be the first to deploy their vaccine.
“To everyone involved in this breakthrough: thank you.
“In years to come, we will remember this moment as the day the UK led humanity’s charge against this disease.”
Scotland’s First Minister Nicola Sturgeon said it was “the best news in a long time”.
She tweeted: “@scotgov ready to start vaccinations as soon as supplies arrive.”
Sir Simon Stevens, chief executive of the NHS in England, said the vaccination programme would be the “largest-scale vaccination campaign in our country’s history”.
In a statement, he said: “This is an important next step in our response to the coronavirus pandemic and hospitals will shortly kick off the first phase of the largest-scale vaccination campaign in our country’s history.
“The NHS has a proven track record of delivering large-scale vaccinations from the winter flu jab to BCG and, once the final hurdles are cleared and the vaccine arrives in England’s hospitals, health service staff will begin offering people this ground-breaking jab in a programme that will expand to cover the whole country in the coming months.”