Background Smoking prevalence among people experiencing homelessness is high. This study explored the factors which influenced potential smoking abstinence among participants receiving an e-cigarette (EC) intervention within the Smoking Cessation Trial in Centres for Homelessness (SCeTCH) across Great Britian.

Methods Using the Capability Opportunity Motivation – Behaviour (COM-B) model, hypothesised and emerging mediators were explored quantitatively via measures in baseline and follow-up questionnaires (n=239) and qualitatively via interviews with homelessness centre staff (n=16) and participants (n=31) who received an EC starter pack and 4-week e-liquid supply. We purposively sampled 8 centres for interviews, representing varied regions and participant vaping/smoking and sociodemographic status. Quantitative measures were analysed descriptively. Qualitative data were analysed thematically. Data from the two approaches were mapped onto the COM-B for combined analysis and reporting.

Results After receiving the intervention, participants demonstrated high capability to use EC and appreciation of EC for harm reduction. Some participants reported dissatisfaction with vaping. Opportunity for behaviour change was strengthened by perceived acceptability to vape and social support beyond the centre but hindered by a smoking culture and perceived lack of staff support. Motivation was enhanced by EC efficacy belief, pride from cutting down, and financial benefits of vaping, but negatively impacted by challenging personal circumstances.

Conclusion For people accessing homelessness support centres, smoking abstinence remains challenging. More intensive support and a variety of approaches to support smoking cessation, particularly those which address the psychosocial factors which hinder smoking abstinence, may be required. Future research should focus on how this can be achieved.

Ford reports financial support was provided by National Institute for Health Research. McMillan, Cox, Soar, Pesola, Notley, Brown, Ward, Gardner, Varley, Mair, Lennon, Brierley, Edwards, Mitchell, Robson, Tyler, Parrott, Li, Bauld, Dawkins reports financial support was provided by National Institute for Health Research. Dawkins reports a relationship with Johnson % Johnson that includes: consulting or advisory. Soar reports a relationship with ThriveTribe that includes: consulting or advisory. Soar reports a relationship with Pharmastrat Ltd that includes: consulting or advisory. Notley reports a relationship with Vox Media that includes: speaking and lecture fees. Bauld reports a relationship with Scottish Government that includes: employment. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

The trial was registered on the ISRCTN registry (ID:18566874)

This work was supported by the National Institute for Health Research (NIHR) Public Health Research Programme (NIHR132158).

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Ethical approval for the study was granted by London South Bank University ethics committee (ETH 2021-0176/2122-0130/2122-0142).

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