A protocol for a cluster randomised feasibility study of an adolescent incentive intervention to increase uptake of HPV vaccination among girls

BACKGROUND Uptake of the human papillomavirus (HPV) vaccine in the UK is good, but there are pockets of the community who remain unprotected. Immunisation teams usually require written parental consent for a girl to receive the vaccine. Evidence suggests that uptake of the vaccine might be improved by promoting consent form return (if returned, forms are likely to grant consent). Incentivising girls to return consent forms is a promising approach to promoting consent form return. Before testing the efficacy of an incentive intervention in a randomised controlled trial (RCT), we must first establish whether the RCT is feasible. In this randomised feasibility study, we aim to establish the feasibility of conducting a cluster RCT of an adolescent incentive intervention to increase uptake of HPV vaccination. METHODS At least six schools will be randomised to either an incentive intervention arm or a standard invitation arm. Girls in standard invitation arm schools will receive the usual HPV vaccine programme invitation materials. Girls attending schools in the incentive intervention arm will receive the standard invitation and will also be told that they will receive an incentive if they return their consent form (regardless of whether consent is granted or denied). The incentive is being entered into a prize draw to win a retail voucher. Feasibility objectives include estimating the schools' and parents' willingness to participate in the study and be randomised; response rates to questionnaires; the extent of missing data; the girls' and parents' attitudes towards the incentive offered; school staff experiences of participating, fidelity to the trial procedures, data on any unintended consequences and the possible mechanisms of action, and proof-of-concept evidence of the effect of the intervention on consent form return rates and uptake of the vaccine. Analysis of feasibility outcomes will primarily be descriptive. Consent form return rates and uptake of the vaccine will be presented by trial arm without comparison. DISCUSSION Incentivising HPV vaccine consent form return may promote HPV vaccine uptake. This study will provide the evidence needed to establish whether testing this incentive intervention using a RCT design in the future is feasible. TRIAL REGISTRATION ISRCTN72136061.