A new clinical trial is to investigate whether a third dose of the Covid-19 vaccine will improve the immune response for people with weakened immune systems.

The government-funded study follows the results of another trial which showed that 89 per cent of people who are immunocompromised or immunosuppressed generate antibodies, while 60 per cent generate a strong antibody response after two doses.

The original study also revealed that 40 per cent of people in these groups mounted a low, or undetectable, immune response after two doses, and the level of antibody response varies between the groups studied.

Participants, followed until mid-2022, will be given Pfizer, Moderna, or Novavax as part of the trial.

The £2.2 million study will build on the previous trial, named OCTAVE, led by the University of Glasgow and co-ordinated by the University of Birmingham’s Cancer Research UK Clinical Trials Unit.

Up to 1,200 patients who are already involved in the OCTAVE study or those with other at-risk conditions involved in parallel studies will be recruited to this latest trial.

The OCTAVE DUO study, co-funded by the government’s Vaccines Taskforce and UK Research and Innovation (UKRI) will analyse in detail the immune response of this group to the vaccine and the durability of this protection.

It will also use healthcare records to determine whether any participants are later diagnosed with Covid-19.

Initial results are expected later this year and will inform the UK’s Covid-19 vaccine deployment in these specific at-risk groups.

“Vaccines have built a strong wall of defence in the UK and this is allowing most of us to learn to live safely with Covid-19,” said Sajid Javid, health and social care secretary. “We know some people may get less protection from the vaccine than others, so we are planning for a booster programme in the autumn, prioritising those most at risk."

The health secretary added: "This new study will play an important role in helping to shape the deployment of future vaccines doses for these specific at-risk groups.”

A separate study by Public Health England (PHE) in July, which looked at antibody response and vaccine effectiveness against symptomatic infection, also showed that those who were immunocompromised had lower antibody responses.

It also found that protection from Covid - vaccine effectiveness against symptomatic disease - for those who are immunosuppressed of all ages after one dose was 4 per cent, and after two doses 74 per cent.

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