The first people in the UK are expected to receive a coronavirus vaccine later, as rollout of the Pfizer/BioNTech jab begins in what is being called “V-day”.
About 70 hospital hubs in the UK are gearing up to vaccinate the over-80s and some health and care staff.
It marks the start of a mass programme aiming to protect the most vulnerable and return life to normal.
More than 60,000 people in the UK have died after being infected with Covid, according to government figures.
The UK will be the first country in the world to start using this vaccine after regulators approved its use last week.
Vaccination will not be compulsory.
Prime Minister Boris Johnson said: “Today marks a huge step forward in the UK’s fight against coronavirus.”
But he added: “As the programme ramps up in the weeks and months ahead, it is as important as ever to keep to the Covid winter plan – following the rules in your area and remember the basics of hands, face and space.”
Ministers have warned it could be Easter by the time restrictions are lifted in a significant way.
Health Secretary Matt Hancock said there was now “light at the end of the tunnel”.
“We will look back on today, V-day, as a key moment in our fightback against this terrible disease,” he added.
The government has secured 800,000 doses of this vaccine to start with, but orders have been placed for 40 million in total, enough for 20 million people as two courses are needed.