Exploring the experiences and perceptions of co-administration of routine vaccines in adults: Findings from an embedded qualitative study with participants and research delivery staff in the ZosterFluCov randomized controlled trial

Vaccine co-administration is common in childhood immunization programmes and helps facilitate the uptake of and adherence to the immunization schedule. There are limited data on the role of co-administration in the adult vaccine schedule and attitudes toward this approach. We aimed to understand the experiences and perceptions of vaccine co-administration of trial participants and study staff members. The study was an integrated qualitative study that formed part of ZosterFluCov, a randomized controlled trial which assessed the immunogenicity of seasonal influenza and COVID-19 vaccines when given with a recombinant zoster vaccine (shingles vaccine). Using semi-structured interviews, we explored the perceptions and experiences of participants and study staff members around vaccine co-administration, and concerns and information needs. We interviewed 20 trial participants and 24 research delivery staff. We found that the co-administration of routine vaccines was highly acceptable amongst the trial participants. Staff viewed vaccine co-administration as within their scope of practice and many had experience of it prior to the trial. Participants from both groups felt that vaccine co-administration could be a time efficient way to administer vaccines, for both health professionals and patients. Vaccine co-administration was regarded as an acceptable method of delivery with the potential to save resources whilst simplifying the process for individuals. The importance of personal preference regarding the number of vaccines was emphasized, whilst staff noted that practical adjustments would be needed for real world delivery. Vaccination co-administration offers the opportunity to optimize vaccine coverage amongst those eligible for routine and seasonal vaccinations.