People in England aged 70 and over, as well as clinically extremely vulnerable ones, will receive offers of a coronavirus vaccine this week.
Prime Minister Boris Johnson said the move was a “significant milestone” in the nation’s vaccination programme.
More than five million people – from priority groups three and four – will be invited to have the jab from Monday.
It comes as 10 new mass vaccination hubs open across England.
The UK has also now closed its travel corridors until at least 15 February to protect against “as yet unidentified new strains” of Covid.
The expansion of the vaccination programme comes after the number of people to receive a first dose rose to 3.8 million across the UK – more than have tested positive (3.4 million) since the pandemic began.
However, people in the top two groups – care home residents, those aged 80 and over and front-line healthcare workers – should still be prioritised for vaccinations, the Department for Health and Social Care said.
People aged 70 and over and clinically extremely vulnerable individuals make up priority groups three and four.
A further 298,087 people received their first dose of the vaccine on Saturday, and Health Secretary Matt Hancock said half of all those aged 80 and over had received at least one vaccine dose so far.
“We are now delivering the vaccine at a rate of 140 jabs a minute and I want to thank everyone involved in this national effort,” said Mr Johnson.
“We have a long way to go and there will doubtless be challenges ahead – but by working together we are making huge progress in our fight against this virus.”
Mr Hancock added: “This measure does not mean our focus on getting care homes, healthcare staff and those aged 80 and over vaccinated is wavering – it will remain our utmost priority over the coming weeks to reach the rest of these groups.”
In a bid to meet the government’s target of offering a vaccine to all 15 million people in the top four priority groups by 15 February, 10 new vaccination hubs are opening in England from Monday, to go with the seven already in use.
While the prime minster said the UK is making “huge progress in our fight against the virus”, he also expressed concern about that progress being derailed by new – currently unknown – variants of the virus.
As such, he announced on Friday that, from this week, all travel corridors are to be closed.
That means that anyone arriving in the UK will have to quarantine. Under current rules, anyone flying into the country from overseas also has to show proof of a negative Covid test before setting off.
The developments come after the UK recorded a further 671 deaths within 28 days of a positive Covid test, and another 38,598 positive tests.
Daily totals for cases and deaths tend to fluctuate due to delays in reporting, but the seven-day average for deaths in the UK is currently 1,119; for cases, it is 46,231.
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