Detailed Description:

Most smokers who made quit attempts and achieved short-term abstinence return to smoking (relapse) over time, even when aided by effective smoking cessation treatment. Since relapse mostly occurred in the first 4 weeks of abstinence, relapse prevention in the early phase of abstinence could potentially boost long-term abstinence. Several behavioural interventions for smoking relapse prevention have been proposed and tested in RCTs. Yet, a 2019 Cochrane review did not find traditional approaches, including self-help materials, telephone counselling and group therapy, effective in increasing long-term abstinence at 6 months or longer. The widespread use of mobile devices has provided a highly accessible and scalable means for novel behavioural interventions for smoking cessation. A formative qualitative study in current smokers conducted by the investigators showed that mobile chat messaging is a feasible and acceptable platform for delivering smoking cessation support. A subsequent cluster randomised controlled trial on 1148 smokers found that mobile chat messaging combined with brief intervention was effective in increasing biochemically validated abstinence at 6 months. Nonetheless, whether mobile chat messaging could prevent relapse in recent abstainers has remained untested. The investigators did a pilot trial to confirm the feasibility and acceptability of mobile chat messaging for relapse prevention in recent abstainers. This study aims to evaluate the effectiveness of mobile chat messaging relapse prevention intervention in promoting abstinence in recent abstainers.}}