Peer-led intervention to prevent and reduce STI transmission and improve sexual health in secondary schools (STASH): protocol for a feasibility study

Background: Young people in the UK are at highest risk of sexually transmitted infections and report higher levels of unsafe sex than any other age group. Involving peer supporters in intervention delivery is acceptable to students and effective in reducing risk behaviours via 'diffusion of innovation', particularly where peer supporters are influential in their networks. Informal peer-led interventions offer a useful alternative to peer-led didactic teaching, which has shown limited effects. Building on the successful ASSIST anti-smoking intervention, the 'STis And Sexual Health' (STASH) intervention involves identification and recruitment of the most influential students as peer supporters, training and support to these students by specialist trainers, positive sex and relationships messages, spread by peer supporters to their friendship groups in person and via social media. Methods/design: This protocol describes a feasibility trial of the STASH intervention in six schools. It builds on an earlier study phase of intervention co-development using patient and public involvement (PPI) activities, followed by a pilot of intervention components and evaluation tools in one school. Participants are fourth year (S4) students (aged 14-16) in state-funded Scottish secondary schools who have received some level of teacher-led sex education. The previous cohort of S4 students (those completing S4 in the year prior to the intervention) will serve as controls. Data will be collected from controls (month 16), baseline (month 20-21) and follow-up (month 27-30) via a web-based questionnaire, which will measure (and test the reliability of) primary outcome measures for a phase III trial (delayed initiation of/abstinence from sex and consistent condom use), secondary outcomes and mediators of sexual behaviour (including school climate and social networks). The main feasibility outcome is whether the study meets pre-set progression criteria regarding feasibility and acceptability, measured largely via a process evaluation (basic measures in all 6 schools and in-depth in 2-4 schools). An economic evaluation reporting costs alongside consequences will be conducted. Discussion: This study will inform decisions on the feasibility, design and sample size for a phase III effectiveness trial to assess whether the STASH intervention is effective in reducing the risk of sexually transmitted infections in young people