A new government-funded clinical trial looking at different Covid-19 ‘booster’ vaccines got underway this week. Initial results from trialling seven vaccines are expected in September to inform plans for a booster programme.

The Cov-Boost study, led by University Hospital Southampton NHS Foundation Trust and backed by £19.3 million of government funding, will be the first in the world to provide data on the impact of a third dose on patients’ immune responses. The study will include a total of 2,886 patients and participants will start being vaccinated from early June.

The initial findings will help inform decisions by the Joint Committee on Vaccination and Immunisation (JCVI) on plans for a booster programme from autumn this year.

The trial will look at seven different Covid-19 vaccines as potential boosters, given at least 10 to 12 weeks after a second dose as part of the ongoing vaccination programme. Vaccines being trialled include Oxford/AstraZeneca, Pfizer/BioNTech, Moderna, Novavax, Valneva, Janssen and Curevac, as well as a control group.

Earlier this year, the government launched the ComCov trial, which aimed to determine the effects of using different vaccines for the first and second dose. Initial results have shown that mixing the doses slightly increases the frequency of mild-to-moderate symptoms following vaccination, but there were no serious outcomes.

Further results from this clinical trial – including on the immune response in people who have two different vaccine doses – are expected over the coming months.