COV-BOOST: A randomised, phase II UK multi-centre study to determine reactogenicity and immunogenicity of booster vaccination against ancestral and novel variants of SARS-CoV-2

Due to concerns that existing COVID-19 vaccines may be less effective against new variant strains and uncertainty on the most effective booster vaccine schedule in March 2021 the COV-Boost trial was set up as the world’s first COVID-19 vaccine booster study. 

This trial is a randomised, phase II UK multi-centre trial which is aimed to investigate a combination of booster vaccines with the vaccines already received by the population to examine their safety profile and immune responses and compare these.

Initially it aimed to establish the reactogenicity and immunogenicity of thirteen experimental arms against ancestral and novel variants of SARS-CoV-2 in participants who have received two doses of AstraZeneca or Pfizer early in the UK NHS deployment campaign.

It has expanded to examine the safety and efficacy of boosting using vaccines designed specifically to target novel variants of the SARS-CoV-2 virus when these vaccines become available and additional questions on fourth dose boosters, timings of vaccine schedules as well as fractional dosing in young adults.