Everyone in Norfolk and Waveney aged 50 and over is being invited to book their coronavirus vaccination.
All those aged 50 to 54 across England have been encouraged to organise appointments via the NHS website.
The age bracket is the final group on the government's vaccine priority list, as recommended by the Joint Committee on Vaccination and Immunisation (JCVI).
Those nine cohorts cover 99pc of those considered to be at high risk of dying in the event of contracting Covid-19.
Some 50 to 54-year-olds in Norfolk and Waveney are known to have received initial doses, while others under the age of 50 have already booked appointments.
Praising the latest milestone, vaccine minister Nadhim Zahawi said the UK was "leading the way".
“Vaccines are the best way out of this terrible pandemic and the NHS is doing everything it can to protect those most at risk as quickly as possible," he added.
“We are on track to offer vaccines to all adults by the end of July and I urge everybody who is eligible to get their jabs to protect yourself and your loves ones.”
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Thus far, almost 25 million adults in the UK have received a first shot, while another 1.6 million have been administered their second.
In the early stages of the rollout, leading politicians estimated that everyone over 50, frontline health workers and those with seriously underlying health conditions would have been offered a jab "by mid-April".
And that target looks likely to be met thanks to a surge in vaccine supply over the coming days, largely down to a significant shipment of Oxford/AstraZeneca doses arriving from the Serum Institute in India.
It means the programme is on course to be two weeks ahead of schedule.
Around two million text messages are now being sent to the latest cohort, accompanied by a link directing them to the national booking system.
Those who are unable to access the website can call NHS England on 119.
Everyone in the top nine priority groups - about 30 million people - should be offered a second injection by the middle of July.
This is a maximum of 12 weeks after the first, a policy designed to maximise the number of people getting a vaccine and therefore receiving protection from the disease.
The second phase of the rollout is split into three groups: 40 to 49-year-olds; 30 to 39-year-olds; and 18 to 29-year-olds.
They are due to be offered an initial dose of the vaccine by the end of July.
On Wednesday morning, health secretary Matt Hancock reassured the public that the Oxford jab is safe following concerns over blood clots.
While a definitive link has not yet been established, several European nations have suspended use of the vaccine while they await the results of further research.
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