Vaccines for people over 40 will begin this month as Britain delivers jabs to more than 20 million adults, The Telegraph reported.
Health officials are about to send the last batch of invites to those over 60, the report added.
More than 20 million people across the United Kingdom have now received their first Covid-19 vaccine shot, data showed on Sunday as the country made more progress with Europe's fastest vaccination programme.
Prime Minister Boris Johnson said the milestone represented "a huge national achievement and he paid testament to the country's health, workers, volunteers and armed forces.
"I urge everyone to get the jab when called," Johnson said. "Every jab makes a difference in our battle against Covid."
Britain has suffered the highest Covid-19 death toll in Europe - it currently stands at 122,849 - and the heaviest economic shock among big rich countries, according to the headline measures of official data.
But the pace of its vaccination roll-out has raised the prospect of a gradual lifting of its current lockdown restrictions between now and the end of June.
On Sunday, finance minister Rishi Sunak promised to help the economy while the country remains under restrictions.
In a budget statement on Wednesday, he is expected to announce more borrowing on top of his almost 300 billion pounds ($418 billion) of Covid-19 spending and tax cuts.
Official data showed a total of 20.09 million people in Britain have received their first dose of a Covid-19 vaccine and almost 800,000 have received a second dose.
Last week, Britain said more than one in three adults had received their first vaccination.
Britain also reported on Sunday a further 6,035 cases within the previous 24 hours, and 144 more deaths within 28 days of a positive test.
The latest figures meant cases over the past seven days were down 21.2% compared with the previous seven-day period of Feb. 15-21, and deaths were down 33.5%.