Online group support potentially help prevent smoking relapse. This two-arm, pragmatic, open-label randomized controlled trial assessed the effectiveness of instant messaging (IM) (i.e., WhatsApp) online group support versus text messages for smoking relapse prevention. The intervention group (n = 469) participated in 8-week counsellor-moderated IM-based online discussion groups and receive messages on preventing relapse via WhatsApp. The control group (n = 459) received similar messages via text messaging for 8 weeks. Primary outcome was biochemically validated tobacco abstinence (exhaled carbon monoxide < 4 parts per million; or saliva cotinine < 10 ng/ml) at 12-month follow-up. By intention-to-treat, intervention and control groups showed similar prevalence of biochemically validated abstinence (11.9% versus 11.7%, risk ratio [RR] = 1.01; 95%CI 0.71–1.44; P = 0.93). The interactive IM-based online group support was costly but did not increase smoking abstinence compared to simple text messaging. More interactive digital health interventions are more costly but may not be more effective than simple text messaging. ClinicalTrials.gov Identifier: # NCT03717051.

在线团体支持可能有助于防止复吸。这项双组、务实、开放标签随机对照试验评估了即时消息 (IM)（即 WhatsApp）在线团体支持与短信预防吸烟复吸的有效性。干预组 ( n  = 469) 参加为期 8 周、由辅导员主持的基于 IM 的在线讨论小组，并通过 WhatsApp 接收有关预防复发的消息。对照组 ( n  = 459) 在 8 周内通过短信收到类似的信息。主要结果是在 12 个月的随访中经生化验证的戒烟情况（呼出的一氧化碳 < 百万分之 4；或唾液可替宁 < 10 ng/ml）。通过意向治疗，干预组和对照组显示出经生化验证的戒断率相似（11.9% vs 11.7%，风险比 [RR] = 1.01；95%CI 0.71–1.44；P  = 0.93）。基于即时消息的交互式在线小组支持成本高昂，但与简单的短信相比并没有提高戒烟率。更具互动性的数字健康干预措施成本更高，但可能并不比简单的短信更有效。ClinicalTrials.gov 标识符：# NCT03717051。