Older British people and medical workers may be given a new version of the Covid-19 vaccine this year which is tailor-made to protect against the Omicron variant.
Ministers hope that the next generation of jabs made both by Pfizer and Moderna will be ready in time for autumn, when a new round of vaccines will be administered to certain groups.
Over-65s, vulnerable people below that age, and frontline health and care workers are due to be invited for another vaccination to top up their immunity levels.
The decision by the Joint Committee on Vaccination and Immunisation (JCVI) to target only those groups came as a surprise to the Government, according to a Whitehall source, because they had expected to offer an additional jab to everyone over 50.
It is possible that the criteria could be widened in the coming months, based on evidence about how quickly the current protection is waning and what difference another dose could do for younger groups.
Health Secretary Sajid Javid is understood to believe there is a significant chance that the new jabs, adapted by their manufacturers to target Omicron specifically, can be used in the autumn booster campaign.
The UK has around 150 million vaccines on order from Pfizer and Moderna, having decided not to use the Oxford/AstraZeneca jab for any further boosters.
Contracts signed by the Government specify that the two US-based firms must deliver whatever is the latest version of their vaccine, meaning Britain should be near the front of the queue for accessing the adapted jabs.
Moderna said this month that a “bivalent” vaccine which is designed to protect against both the original coronavirus detected in Wuhan, and the Omicron variant which emerged at the end of last year, was its “lead candidate” to be used from the autumn onwards.