People aged 34 and over can book their Covid-19 jab from Thursday, the NHS in England has said.
More than one million people aged 34 and 35 will get a text message on Thursday or Friday asking them to come forward for their Covid vaccine, NHS England said.
The vaccination programme is expected to extend to people in their early thirties “over the next few days and weeks”, it added.
Health officials have sped up the timetable to offer second jabs in a bid to ensure that those at highest risk are protected from the variant of the virus first identified in India.
At the same time, the programmes are extending to younger age groups to try and mitigate risk.
Professor Stephen Powis, national medical director for the NHS in England, said: “The success of the NHS Covid-19 vaccination programme, the biggest in history, is not by accident but down to careful planning and precision by NHS staff who have now delivered 48.5 million doses across England in less than six months.
“Getting the vaccine is the single most important step we can take to protect ourselves, our families and our communities against Covid 19, so when you’re called forward, book your appointment and join the tens of millions who have already been jabbed.”
Health and Social Care Secretary Matt Hancock said: “Our vaccination programme – the fastest and most successful in NHS history – moves forward at pace with 34 and 35-year-olds now being invited for the jab.
“This is incredible news and means we remain on track to hit our target of offering a vaccine to all adults by the end of July.
“The vaccine is our way out of the pandemic and the key to getting back to normal.
“I’m delighted that 70% of adults across the country have already been vaccinated with their first dose, and 40% with their second.
“We have one of the highest uptake rates in the world but we’ll continue to do everything we can to make sure no one is left behind. Please come forward for the jab once you get the offer – it could save your life and protect your loved ones.”
Vaccination experts have previously advised that people under the age of 40 should receive an alternative vaccine to the Oxford/AstraZeneca jab due to the link between the jab and extremely rare cases of blood clots.
This means that most under 40s will be offered the Pfizer or Moderna vaccines.
Figures released by the Department of Health and Social Care on Wednesday show that health services across the UK had administered 57.8 million vaccines, including 36.9 million people with their first dose – or 70.2% of the adult population.
Meanwhile, 20.8 million people – almost two-fifths (39.6%) of the adult population – had received both doses.
The news comes it was announced the vaccination programme in Northern Ireland was extending to include people aged 25 and over.
NHS leaders in Scotland are encouraging people aged 30 and over to come forward for their jab.
In Wales, some 43% of 18 to 29-year-olds have had their first jab and 62% of those aged 20 to 39 have had their first dose.