A single-blind, phase IV UK multi-centre randomised controlled trial to determine reactogenicity and immunogenicity of COVID-19 vaccines administered concomitantly with seasonal influenza vaccines

Mass vaccination against COVID-19 started in the UK in early December 2020 and is likely to continue until mid-2021. Whilst rates of COVID-19 infection have decreased, the emergence of variants of interest and planned easing of lockdown measures has led to predictions of potential resurgence of infection from autumn 2021. The duration of protection of the current COVID-19 vaccines is unknown but it may be that further booster doses will be required in 9 to 12 months time with current or potentially strain-modified vaccines to afford continued protection into the autumn. The timing of the booster doses is likely to coincide with seasonal influenza vaccination, which is usually September to February. Delivering COVID-19 and influenza vaccines at separate appointments will cause significant logistical challenges therefore it would be desirable to immunise with both vaccines at the same appointment, in different arms. The ComFluCOV trial will determine the safety, as well as the immune responses, to administration of the currently approved COVID-19 vaccines at the same time as the recommended influenza vaccines from the 2020/21 season. Participants who are having their second COVID-19 vaccine will be randomised into two groups; one group will receive the influenza vaccine and the other group will receive saline (placebo) at the same time as the COVID-19 vaccine. Participants will not know whether they receive the influenza vaccine or the placebo. After 3 weeks participants who received the influenza vaccine will receive the saline injection and participants who received the saline injection will receive the influenza vaccine. Participants will be followed up for a further 3 weeks after the second injection. We hope to recruit 504 participants into the trial. The trial will be conducted in at least 5 UK NHS centres. The trial is expected to take about 6 months to complete.