A Covid booster jab will probably be required to protect a small number of the most vulnerable people, but a mass rollout may not be needed, a senior government adviser has said. Prof Adam Finn, who sits on the Joint Committee on Vaccination and Immunisation (JCVI), said it was still unclear whether all over-50s should be given a third shot after the health secretary, Sajid Javid, said plans were in place to offer the whole cohort a booster. “We’ve been asked to advise as to who might receive a booster if it proves necessary to give boosters,” Finn told BBC Breakfast on Wednesday. “I think it’s becoming quite clear that there are a small group of people whose immune responses to the first two doses are likely to be inadequate – people who’ve got immunosuppression of one kind or another, perhaps because they’ve got immunodeficiency or they’ve been receiving treatment for cancer or bone marrow transplants or organ transplants, that kind of thing. I think it’s quite likely we’ll be advising on a third dose for some of those groups. “A broader booster programme is still uncertain, we’ve laid out potential plans so that the logistics of that can be put together, alongside the flu vaccine programme. “We need to review evidence as to whether people who receive vaccines early on in the programme are in any serious risk of getting serious disease and whether the protection they’ve got from those first two doses is still strong – we clearly don’t want to be giving vaccines to people that don’t need them.” The booster vaccination programme is due to start on 6 September, but the JCVI – the expert panel that advises the government – is still assessing hospital admissions data and blood test samples before it approves the programme. On Tuesday, Javid said the government was awaiting the JCVI’s advice, but indicated the plan would probably be for over-50s to be offered the booster at the same time as a flu jab. He said those who got their jabs when the vaccine programme began in December last year would be prioritised.