People aged 30 and 31 in England are being invited to book to have their first dose of Covid vaccine.
The NHS is urging these million or so to take up the offer of a jab at one of the 1,600 available locations, including mosques, museums and rugby grounds, as well as pharmacies.
Nearly three-quarters of adults in the UK have already had one dose, and more than two-fifths have had two.
The government plans to offer first doses to all adults by the end of July.
Two doses are needed for strong protection against Covid, particularly the variant first found in India - also known as B.1.617.2 - that is driving some regional outbreaks in parts of the UK.
Over-50s and those considered clinically vulnerable are having their second doses brought forward to eight weeks after their first - rather than 12 - following concerns about the variant.
Surge testing is also happening, to try to stop it spreading.
Guidance for Bedford, Blackburn with Darwen, Bolton, Burnley, Kirklees, Leicester, Hounslow and North Tyneside says people in these areas should try to avoid meeting indoors, as a precaution.
Health and Social Care Secretary, Matt Hancock said: "Our vaccination programme is moving at such a phenomenal pace and I am delighted that less than six months after Margaret Keenan received the first authorised jab in the world, we are now able to open the offer to everyone in their thirties and over.
"I want to say a huge 'thank you' to everyone who has rolled up their sleeves to help us roll out this life-saving jab. The NHS is booking record numbers of appointments and it is fantastic to see the public come forward in such exceptional numbers."
People who cannot go online to book can call the service on 119 instead.
People aged 39 and under who are eligible, and pregnant women, will be offered the Pfizer or Moderna vaccine.