Some people may need a fourth dose of Covid vaccine to remain protected, a government scientific adviser has said, with a decision expected shortly after the Christmas and new year holidays.

Prof Adam Finn said: “I think there may well be people who received their boosters early who are in the older more vulnerable age groups who may need a further jab. That has not been decided yet. It is still under review and discussion, and we will be providing recommendations on that at some point in the new year.”

Finn, a professor of paediatrics at the University of Bristol and a member of the Joint Committee on Vaccination and Immunisation (JCVI), told LBC Radio on Thursday: “I think there will be people probably who will receive a fourth jab. Whether that will be everyone, I think, is still very much in doubt … We do need to see how things go through this wave and beyond.”

On Tuesday, Israel became the first country to announce it would offer a fourth dose of vaccine to people over 60 and healthcare workers, in an effort to increase protection against the Omicron variant.

The country’s prime minister, Naftali Bennett, urged those eligible to “go and get vaccinated” in a rollout expected over the next few days.

Finn also raised the possibility of vaccinations for all children aged five to 11. He said the move was still under “very active consideration”, but that there were “very, very few severe cases” in the age group. The government had originally introduced vaccination for older children to prevent disruption to education and reduce transmission rates.

With the Omicron variant, however, “the ability of the vaccines to do that will be reduced”, he said.

A government-backed study published on Wednesday found that Covid infections among five to 11-year-olds were three times more prevalent than in the general population.

React-1, a joint study by Imperial College London and Ipsos Mori, found an estimated 4.47% of primary school-aged children had the virus, compared with 1.41% across the population as a whole.

The JCVI recommended vaccinations for about 330,000 five to 11-year-olds on Wednesday. It updated its advice after the UK’s Medicines and Healthcare products Regulatory Agency approved the move after a robust review of safety data.

A low-dose version of the Pfizer-BioNTech vaccine will be offered to those in the age group who are clinically vulnerable, or who are a household contact of someone who is immunosuppressed. They will be offered a primary course of vaccination, which is typically two doses.