A new clinical trial is set to launch in the UK to evaluate the ability of a third Covid-19 vaccine dose to improve the immune response in immunocompromised or immunosuppressed individuals with weakened immune systems.

Named OCTAVE DUO, the trial will involve inoculation with Pfizer , Moderna or Novavax Covid-19 vaccines.

Earlier this month, the US Food and Drug Administration revised emergency use authorizations (EUAs) for the Pfizer-BioNTech and Moderna vaccines to enable the use of a third dose in some immunocompromised people.

The £2.2m OCTAVE DUO trial will test if the third vaccine dose can provide a stronger immune response compared to two doses in this patient population.

Apart from immune response, it will assess the durability of vaccine protection. Healthcare records will later be checked for any subjects who went on to develop Covid-19.

Led by the Universities of Glasgow and Birmingham, the trial is co-funded by the UK Government’s Vaccines Taskforce and UK Research and Innovation (UKRI).

OCTAVE DUO builds on the OCTAVE trial, which revealed that two vaccine doses led to antibodies in 89% of immunocompromised or immunosuppressed individuals while 60% had a robust antibody response.

But 40% of the OCTAVE participants experienced a low or undetectable immune response following two doses. The antibody response level was also different between the study groups.

The new OCTAVE DUO trial will enrol up to 1,200 participants who are part of the OCTAVE trial or those who have other at-risk conditions and are part of parallel studies.

Preliminary data from OCTAVE DUO are anticipated this year and may inform the country’s Covid-19 vaccine deployment in these at-risk populations.

University of Birmingham Cancer Research UK Clinical Trials Unit director Pam Kearns said: “Together with our preliminary findings from OCTAVE, this new study will be instrumental in helping inform how best to vaccinate patients with chronic conditions, and protect them from Covid-19 infection in the future.”

In May 2021, the UK launched the Cov-Boost clinical trial to assess the effect of a third ‘booster’ dose of seven different Covid-19 vaccines on patients’ immune responses.

Pfizer-BioNTech, Moderna and Novavax vaccines are included in Cov-Boost.