Background Young people report higher levels of unsafe sex and have higher rates of sexually transmitted infections than any other age group. Schools are well placed to facilitate early intervention, but more effective approaches are required. Peer-led approaches can augment school-based education, but often fail to capitalise on mechanisms of social influence. The potential of using social media in sexual health has not been tested in school settings. Objectives Finalise the design of the Sexually Transmitted infections And Sexual Health (STASH) intervention; assess the recruitment and retention of peer supporters, and acceptability to participants and stakeholders; assess the fidelity and reach, in addition to the barriers to and facilitators of, implementation; refine programme theory; understand the potential of social media; determine design parameters for a future randomised controlled trial, including economic evaluation; and establish whether or not progression criteria were met. Design This was a feasibility study comprising intervention development and refinement of the STASH pilot and non-randomised feasibility trial in six schools. Control data were provided by students in the year above the intervention group. Setting Secondary schools in Scotland. Participants Students aged 14–16 years, teachers and intervention delivery partners. Interventions The STASH intervention was adapted from A Stop Smoking In Schools Trial (ASSIST) (an effective peer-led smoking intervention). Based on diffusion of innovation theory, the STASH study involves peer nomination to identify the most influential students, with the aim of recruiting and training 15% of the year group as peer supporters. The peer supporters deliver sexual health messages to friends in their year group via conversations and use of Facebook (www.facebook.com; Facebook, Inc., Menlo Park, CA, USA) to share varied content from a curated set of web-based resources. Peer supporters are given support themselves via follow-up sessions and via trainer membership of Facebook groups. Main outcome measures The primary outcome was whether or not progression criteria were met in relation to intervention acceptability and feasibility. The study also piloted indicative primary outcomes for a full-scale evaluation. Data sources Peer supporter questionnaire; observations of activities; interviews with trainers, teachers, peer supporters and students; monitoring log of peer supporter activities (including on Facebook and meeting attendance); questionnaire to control year group (baseline characteristics, social networks, mediators and sexual health outcomes); baseline and follow-up questionnaire (approximately 6 months later) for intervention year group. Results A total of 104 students were trained as peer supporters (just over half of those nominated for the role by their peers). Role retention was very high (97%). Of 611 students completing the follow-up questionnaire, 58% reported exposure to STASH study activities. Intervention acceptability was high among students and stakeholders. Activities were delivered with good fidelity. The peer supporters were active, representative of their year group and well connected within their social network. Carefully managed social media use by peer supporters augmented conversations. A primary outcome of ‘always safer sex’ was identified, measured as no sex or always condom use for vaginal or anal sex in the last 6 months. The intervention cost £42 per student. Six progression criteria were met. A seventh criterion (regarding uptake of role by peer supporters) was not. Limitations Small feasibility study that cannot comment on effectiveness. Conclusions The STASH intervention is feasible and acceptable within the context of Scottish secondary schools. The results support continuation to a full-scale evaluation. Future work Small-scale improvements to the intervention, refinement to programme theory and funding sought for full-scale evaluation. Trial registration Current Controlled Trials ISRCTN97369178. Funding This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 8, No. 15. See the NIHR Journals Library website for further project information.

BackgroundYoung 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/designThis 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.DiscussionThis 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.Trial registration ISRCTN97369178