Four in 10 people who have weakened immune systems show 'low or undetectable' levels of Covid immunity after being double vaccinated, a major UK study has found.
The finding will put pressure on the Government's scientific advisers to green light a booster jab programme for the most vulnerable Britons this autumn.
Researchers from the Universities of Glasgow and Birmingham measured antibody levels in 600 immunosuppressed people and compared them to healthy volunteers.
About one in 10 in the vulnerable group failed to generate any detectable Covid antibodies four weeks after their second dose of Pfizer or AstraZeneca.
A further 30 per cent generated a significantly lower antibody response than healthy people, according to the study published as a pre-print in The Lancet.
The scientists stressed that almost all of the people who did not show an antibody response had vasculitis, a condition which causes inflammation of blood vessels.
They added that across almost all patients, the T cell response was similar to healthy adults, indicating that they were at least partially protected against Covid.
While antibodies are the most obvious indicator of immunity, T cells - a type of white blood cell - also play a crucial role in priming the body against the disease.
The experts behind the study have called for the Joint Committee on Vaccination and Immunisation (JCVI) to approve booster doses for the immunocompromised in the coming weeks.
Britain's daily Covid infections, deaths and hospital admissions have been climbing slowly but steadily for several weeks which has raised fears of a fresh wave when schools go back and strengthened the argument for boosters.
Researchers from the Universities of Glasgow and Birmingham measured antibody levels in 600 immunosuppressed people and compared them to healthy volunteers. About one in 10 in the vulnerable group failed to generate any detectable Covid antibodies four weeks after their second dose of Pfizer or AstraZeneca . A further 30 per cent generated a significantly lower antibody response than healthy people, according to the study published as a pre-print in The Lancet
Immunosuppressed people include those with certain types of arthritis, inflammatory bowel disease and some cancers.
Sources say the JCVI is prepared to rollout third doses to this group from September, but will hold back on a mass booster campaign to entire age groups and wait on more evidence of the benefit.
To determine how much protection immunosuppressed people had from the vaccines, researches examined the antibody and T cell levels in 600 of them before a vaccine, after one dose and after both jabs. They compared this with samples taken from 231 healthy individuals.
Four weeks after receiving a second dose, 100 per cent of healthy Brits produced antibodies.
