Those aged over 70 and the clinically extremely vulnerable will be invited to receive coronavirus vaccinations starting this week.
More than 3.8 million people, including those over 80, care home residents, and NHS staff, have already had the first dose of a COVID-19 vaccine.
But from Monday, the programme will be rolled out for the next two priority groups.
The first two groups will remain the priority but vaccination sites that have supply and capacity will be allowed to vaccinate those in the third and fourth groups as well.
It comes as the national vaccine programme continues to expand, with 10 more mass vaccination centres due to open on Monday and the government revealing on Sunday that the vaccine is being given at a rate of 140 per minute.
There are already seven mass vaccination sites across the country, as well as 1,000 GP-led surgeries and more than 250 hospitals providing jabs.
The aim is for 88% of those most at risk of dying from coronavirus to receive their first jab by the middle of February, and 99% of this group by early spring.
On Sunday, Foreign Secretary Dominic Raab told Sky News that all UK adults should be offered the first dose of a COVID vaccine by September – with the hope some restrictions can be lifted by March.
Speaking on Sophy Ridge on Sunday, the foreign secretary said: “Our target is that by September to have offered all the adult population a first dose, if we can do it faster than that great but that’s the roadmap.”
Speaking about the expansion of the vaccine programme, Prime Minister Boris Johnson said: “Today is 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.”
Health Secretary Matt 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.”
On Sunday, 671 deaths within 28 days of a positive COVID-19 test were reported, bringing the total to just under 90,000.
There were also 38,598 new cases reported, the lowest number seen so far this year.