Those aged 32 and 33 in England are being invited to book their first Covid vaccine dose.
One million people in the age group will be able to secure an appointment from 7am on Saturday 22 May, the NHS has said.
Text message invitations will be sent out to 33-year-olds from that day, while those aged 32 should receive one from Monday.
It comes as NHS England is expected to have administered more than 50 million doses by this weekend, with more than 40% of adults in the country having received both their vaccines.
‘Incredible step forward’
Since eligibility was widened for people under 40 just over a week ago, 2.6 million more bookings have already been made, the NHS has said.
Health Secretary Matt Hancock has said extending the rollout to 32 and 33-year-olds is “an incredible step forward in the biggest and most successful vaccination programme in NHS history” and urged people to get their jab when contacted.
Mr Hancock added: “This is truly a testament to the heroic work of our amazing NHS and care staff, volunteers and local authorities across the country who have helped deliver over 50 million jabs at lightning speed across England, keeping us on track to offer a vaccine to everyone by July.
“The vaccine has already saved thousands of lives and you are far less likely to get symptoms or be admitted to hospital if you get the jab.”
NHS chief executive Sir Simon Stevens said that over half of people aged 35 to 39 have now had their first jab.
He added: “Today, the biggest NHS vaccination programme in history hits another milestone as we pass 50 million life-saving jabs delivered across England.”
People encouraged to come forward and book
GP and national medical director for primary care Dr Nikki Kanani reminded people that they can take up their offer for a jab at any time.
Dr Kanani said: “It is fantastic to see so many people come forward so quickly to get their life-saving Covid vaccine – this action means that we are protecting our communities against the virus.
“The offer doesn’t go away so if you are eligible and haven’t booked, please do come forward and do so.
“It is safe, effective and will protect you and those around you.”
On the advice of the government and Joint Committee on Vaccination and Immunisation (JCVI), people aged 50 and over and the clinically vulnerable are also having their second doses brought forward to counter the spread of the Indian variant.
People aged 39 and under who are eligible and pregnant women will be offered the Pfizer or Moderna vaccine in line with recently updated JCVI guidance.
The NHS is urging everyone who is eligible to take up their jab at one of the 1,600 locations across the country.
Text invitations appear as an alert from ‘NHSvaccine’, including a web link to the NHS website to reserve an appointment.
People who cannot go online can call the service on 119 instead to book their jab.