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 British department of health and social care spokesman said: "The Government has today accepted the recommendation from the independent Medicines and Healthcare products Regulatory Agency (MHRA) to approve Pfizer/BioNTech's Covid-19 vaccine for use.
"This follows months of rigorous clinical trials and a thorough analysis of the data by experts at the MHRA who have concluded that the vaccine has met its strict standards of safety, quality and effectiveness."
UK health secretary Matt Hancock told Sky News: "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."
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."