The over-30s are expected to be invited for their Covid jabs in the next fortnight after vaccinations roll out to the over-40s this week.
Half a million 44-year-olds will be told by text they can sign up from today, with the move to those aged 40 to 43 set out later in the week.
Talks continue over whether those in their 30s will receive the AstraZeneca jab, amid blood clot fears.
The roll-out increases the chances of younger people qualifying for vaccine passports that could allow them to travel abroad this summer.
Over 33.5 million people have had their first dose – over 63.5% of UK adults. Some 12 million, or 22.8%, have had both jabs.
Scotland today opens its borders to visitors from England and Wales, allowing friends and families to reunite for the first time in months.
A campaign launches today urging under-50s to get the jab. The first TV ad airs tonight during Emmerdale.
Thor Porter, 32, a drummer of Salisbury, Wilts, who appears in it, said: “It will hopefully enable venues to reopen.”
Vaccines minister Nadhim Zahawi said: “It’s vital as many people as possible book their vaccine.”
Officials are understood to be close to a deal to buy tens of millions more Pfizer doses in time for a booster dose for OAPs this autumn.
A Government adviser has slated calls from anti-lockdown scientists to end restrictions entirely as limits on social contact lift in June.
Prof Stephen Reicher of the advisory Scientific Pandemic Insights Group on Behaviours said: “Don’t let these siren voices lead us back into lockdown.”
