Covid-19 vaccinations for the over-70s and clinically extremely vulnerable people are set to begin, with people in these two categories receiving invitations to get their jabs from Monday.
The government has hailed the next step in its vaccination rollout a “significant milestone”.
It is another step toward the government achieving its goal of vaccinating the top four most vulnerable groups by mid-February, which the government hopes will allow it to begin easing off some lockdown restrictions.
It comes as new travel rules come into force in a bid to keep out dangerous new Covid variants, such as those discovered in Brazil and South Africa.
From 4am on Monday, arrivals into the UK will need to self-isolate for 10 days, or receive a negative result from a coronavirus test taken at least five days after they enter the UK.
Foreign Secretary Dominic Raab said on Sunday that checks at the border would be strengthened as the new measures enter into effect, and vowed to "beef up" capacity to ensure people are adhering to quarantine rules.
But the government faced criticism from Professor John Edmunds, a member of the Government's Scientific Advisory Group for Emergencies (Sage), who said the approach to quarantining foreign arrivals and contacts of coronavirus cases had been "pretty lax" so far.
More than 3.8 million people – including over-80s, care home residents and NHS and social care staff – have already received their first dose of a Covid-19 vaccine, but from Monday it will be rolled out in the next two priority groups.
The government said it would remain the priority to vaccinate those in the first two groups, but that sites which have enough supply and capacity to vaccinate more people will be allowed to offer jabs to the next two cohorts.
Boris Johnson has pledged to offer vaccinations to the first four priority groups by the middle of next month, while Dominic Raab said on Sunday that all adults would be offered a first dose by September.
Once everyone in the top nine groups have been offered a vaccine, the focus will turn to phase two of the rollout, which will see a drive to inoculate the rest of the population.
The government has said it expects teachers and police officers to be among the first offered a jab in phase two of the rollout, but others such as shop workers are being considered.
Vaccines minister Nadhim Zahawi said he thinks there is justification for those who cannot work from home to be prioritised as the vaccination programme develops.
Speaking to ITV’s Good Morning Britain, he said: “My instinct is that anyone who, through no fault of their own, has to come into contact with the virus in much greater volume and probability should be protected – teachers, policemen and women, shop workers, all those who need that additional protection.
“Now, some of them will be captured in the top nine categories anyway if they are clinically vulnerable, for example, or in that age group of the over-50s which are in category nine, effectively.
“But phase two – of course we’ll be guided by the JCVI – but my instinct is that if you work in a job, a shop worker, policemen or women, any other profession which brings you into contact with the virus unfairly, then I think you should be prioritised.”
Also this week, 10 further mass vaccination centres will open in England, with more than a million over-80s invited to receive their coronavirus jab.
Blackburn Cathedral, St Helens rugby ground, Norwich Food Court and a park-and-ride outside York are among the new locations where large-scale vaccination will take place from Monday.
NHS England said they will join the seven existing mass vaccination sites across the country, alongside a thousand GP-led surgeries and more than 250 hospitals already providing jabs.
Prime Minister Boris Johnson hailed the next step in the UK's vaccination rollout as a "significant milestone in our vaccination programme as we open it up to millions more people who are most at risk from Covid 19.
“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.
“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.”
Listen to our coronavirus podcast
Health Secretary Matt Hancock added: “Now that more than half of all over-80s have had their jab, we can begin vaccinating the next most vulnerable groups.
“Where an area has already reached the vast majority of groups 1-2, they can now start opening up the programme to groups 3-4.
“We are working day and night to make sure everyone who is 70 and over, our health and social care workers and the clinically extremely vulnerable are offered the vaccine by the middle of February and our NHS heroes are making huge strides in making this happen.
“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.”
Elsewhere in the UK, more people are now in hospital with coronavirus in Scotland than at any time during the pandemic - despite new infections falling to the lowest level in almost three weeks.
People in Wales were urged to stick to coronavirus lockdown rules as the "significant task" of vaccinating adults continues.
And in Northern Ireland, a health trust boss said the hospital system is facing huge pressure as it braces for the peak of Covid-19 patients needing intensive care treatment.
In other developments:
– NHS England chief executive Sir Simon Stevens said that a coronavirus patient is admitted to hospital “every thirty seconds” – but that the health service is vaccinating at a rate of “140 jabs a minute”.
– Another 671 deaths of people who died within 28 days of testing positive for Covid-19 were reported on Sunday, while there were a further 38,598 lab-confirmed cases of coronavirus in the UK.
– Boris Johnson will face intense pressure from Labour and Tory MPs to extend the temporary £20-a-week uplift to Universal Credit which was given to help families through the Covid crisis.
Listen to the ITV News Politics Podcast:
Who are the priority groups?
The vaccine will be distributed to these groups in the following order, according to the list drawn up by the Joint Committee on Vaccination and Immunisation.
In brackets is the estimated number of people in each group in the UK:
1 - Residents in a care home for older adults and their carers (800,000 people)
2 - Those aged 80 and over and frontline health and social care workers (a total of 7.1 million people in this group: 3.3m over 80s, 2.4m healthcare workers, 1.4m social care workers)
3 - Those aged 75 and over (2.3 million
4 - Those aged 70 and over and clinically extremely vulnerable individuals (3.2 million)
5 - Those aged 65 and over (2.9 million)
6 - All individuals aged 16 to 64 with underlying health conditions which put them at higher risk of serious disease and mortality (7.3 million)
7 - Those aged 60 and over (1.8 million)
8 - Those aged 55 years and over (2.4 million)
9 - Those aged 50 years of age and over (2.8 million)