Booster jabs are to be offered to all adults, with a recommendation by the Joint Committee on Vaccination and Immunisation expected within days, The Daily Telegraph understands.
On Saturday the Prime Minister announced that he had asked scientists to consider extending the rollout of third jabs to everyone aged 18 and over.
He has also asked the JCVI to consider cutting the wait for a booster jab from six months to five and whether 12 to 15-year-olds should now be offered a second dose.
The committee is expected to recommend in favour of the mass expansion of boosters to all adults, meaning a further 13 million people would be eligible, a health source said.
On Sunday the deputy chairman of the JCVI said offering boosters to younger groups and cutting the interval between second jabs and boosters would be a “sensible strategy”.
So far 17,581,331 booster jabs have been administered. Last week, 2,488,015 third jabs were administered. At that pace it would take an estimated 14 weeks to give booster injections to all over-18s.
Until now, boosters have only been recommended for those aged 40 and over. Bookings opened up to some of those in this group last week.
Expanding the rollout to all over-18s would mean a further 13 million people were eligible for a third dose.
The vast majority of those aged 50 and over are due to have boosters by Christmas. But a significant change in the speed of rollout could only be achieved if the gap between doses was reduced to five months, which ministers are keen to see.
On Saturday Boris Johnson said: "We don't yet exactly know how effective our vaccines will be against omicron, but we have good reasons for believing they will provide at least some measure of protection. And if you are boosted your response is likely to be stronger.”
Scientists say that while the new variant might evade antibodies, it would be less likely to escape T-cells and other parts of the immune system which provide broader protection and prevent serious disease.
Prof Anthony Harnden, deputy chair of the Joint Committee on Vaccination and Immunisation (JCVI) yesterday said accelerating the booster programme by extending the eligible age and reducing the interval between doses "will be a sensible strategy".
On Sunday the deputy chairman of the JCVI said over-18s would receive a booster "earlier" than previously envisioned.
Professor Anthony Harnden also said accelerating the booster programme by extending the eligible age range and reducing the interval between the second and booster doses "will be a sensible strategy".
Meanwhile the Health Secretary Sajid Javid told The Andrew Marr Show on the BBC that he has "asked the NHS to prepare for much greater capacity in our vaccination programme".
Prof Harnden told Radio 4's Broadcasting House: "I think there's a very good, strong argument for raising the antibody level in the whole of the community.
"So, accelerating the booster programme, both by extending the age range and by reducing the interval between the second dose and the booster dose, will be a sensible strategy."
When pushed on whether people aged 18 and over would be invited to get the booster sooner, he added: "Those adults 18 plus will have an offer of a booster earlier than we had previously envisaged."
Children aged between 12 to 15 are currently only offered one dose of the Covid vaccine
Earlier this month, the JCVI recommended second jabs for 16 and 17-year-olds, with a 12-week gap between doses.
One of its members said then that it was likely the committee would recommend second doses for 12 to 15-year-olds, with the same interval.
The JCVI has been cautious about recommending second doses to children, because of concerns over the risks of a rare type of heart inflammation.
Children aged between 12 to 15 are currently only offered one dose of the Covid vaccine.
The precaution was taken because of evidence from other countries linking most cases of myocarditis to second jabs. However, most countries have shorter intervals between doses.
JCVI member Adam Finn has said the rollout of jabs to adults in Britain - with a gap of between eight and 12 weeks - suggests that with a longer interval, there is almost no risk of myocarditis.
The rollout of vaccines to secondary school pupils has been slowed by a change in the guidance, with children who have been infected with Covid told to wait three months before receiving their first jab.
On Friday, Prof Chris Whitty warned that schools were seeing “very significant disruption”, especially among primary school pupils and those in the first years of secondary school.