TWO million over-60s will be invited to get their Covid vaccine today, while some over-40s are expected to get the jab this month.
Letters will be sent out to people older than 60 asking them to book their jabs.
🦠 Read our coronavirus live blog for the latest news & updates...
It comes as a staggering 20 million Brits have now received a Covid jab, with Health Secretary Matt Hancock hailing the "magnificent achievement".
By the end of this week all of those in the top seven priority groups will have been contacted about getting the vaccine.
Over-50s could be offered the jab as early as next week, according to NHS England.
Britain is on track to offer the vaccine to everyone older than 50 by the middle of this month, which is a month earlier than the original target.
Over-40s are expected to be contacted later in March.
The total jab figure comes just a fortnight after the UK smashed its target of 15 million vaccines by February 15 a day early.
The achievement is a huge boost in the fight against the bug as lockdown begins lifting from March 8.
Hopes of easing the national shutdown hinges on protecting the most vulnerable groups by spring to beat faster-spreading variants.
Health Secretary Matt Hancock said: "I’m delighted more than 20 million people across the UK have now been vaccinated.
"A magnificent achievement for the country.
"The vaccine is our route out. When you get the call, get the jab."
Boris Johnson also praised the stunning effort.
The PM said: "20 million people across the UK have now got the jab – a huge national achievement and a testament to the tireless work of NHS staff, volunteers, the Armed Forces and many more.
"I urge everyone to get the jab when called. Every jab makes a difference in our battle against Covid."
While Vaccines Minister Nadhim Zawahi tweeted: "BINGO! One Score...over 20,000,000 people have had the vaccination (first dose).
"What an achievement for February 2021. What a team! Proud to be with you on this journey @NHSuk".
The impressive progress has put the UK as one of the global frontrunners when it comes to the vaccine.
The Government has now set the Herculean task of giving ALL adults a first dose by the end of July.
It comes after figures showed a single dose of a coronavirus vaccine can reportedly give 90 per cent protection from the disease.
As a result, the jabs are slashing hospitalisations.
SILENT PROTESTMeghan cradles bump during Oprah chat when asked if she was 'silenced'
'MY FEAR'Harry tells Oprah he left UK as he feared Meghan would suffer same fate as Diana
LESSONS CUTSchools could scrap 'live' online classes for 2 weeks to test secondary pupils
MUTANT HUNTDesperate search launched for MISSING UK patient with Brazilian Covid strain
TREVOR KAVANAGHEven lefties are talking about just how well our Tory government is doing
AIR HEADLabour deputy leader Angela Rayner claimed £249 personalised Apple AirPods on exes
The results apply to the Pfizer and Oxford/AstraZeneca vaccines, with the British jab proving slightly more effective against the bug.
The figures, taken from a study based in England, were calculated by comparing people who had received a first dose of the jab with others of a similar age who had not got their vaccine yet.
And researchers say the Oxford/AstraZeneca jab is more effective than Pfizer's vaccine at stopping people from becoming severely ill and needing to be hospitalised, the Mail on Sunday reports.