A multi-centre cluster randomised controlled trial evaluating the effectiveness of e-cigarettes compared with usual care for smoking cessation when offered to smokers accessing homeless services: methodological challenges and experiences of collaboration.

Around 80% of people experiencing homelessness smoke. E-cigarettes (ECs) are an effective quitting aid, but they have not been widely tested in this population. Project SCeTcH aims to evaluate the offer of an EC or usual care (UC) to smokers accessing homeless centres. A multi-centre two-arm cluster randomised controlled trial (RCT), including 32 homeless centres across Great Britain (480 participants). Randomisation includes either an EC with weekly allocations of e-liquid for 4-weeks or UC comprising very brief advice and signposting to a stop smoking service. After year 1, 27 centres and 240 participants have been recruited and retention rates at 4- and 24- weeks are 67% and 70% respectively. Challenges include working with multiple centres with different structures, provision, and client needs; reconciling risk of bias with the practicalities of working in this sector; the ongoing impact of Covid; changing models of care and practice; and juggling the needs of different collaborators researchers and health and social care organisations This is the first cluster RCT to assign smokers experiencing homelessness to an EC and UC intervention to measure smoking abstinence and risky smoking practices. Running trials in this population requires the need to understand the realistic needs of these individuals and services, and to work pragmatically and flexibly within the remit of the trial protocol. Ultimately, if effective, the results will be used to inform the larger scale implementation of supporting homeless centres to aid smoking cessation.