Objective Most smokers who achieve short-term abstinence relapse even when aided by evidence-based cessation treatment. Mobile health presen
Objective Most smokers who achieve short-term abstinence relapse even when aided by evidence-based cessation treatment. Mobile health presents a promising but largely untested avenue for providing adjunct behavioral support for relapse prevention. This paper presents the rationale and design of a randomized controlled trial aimed at evaluating the effectiveness of personalized mobile chat messaging support for relapse prevention among people who recently quit smoking. Methods This is a two-arm, assessor-blinded, randomized controlled trial conducted in two clinic-based smoking cessation services in Hong Kong. An estimated 586 daily tobacco users who have abstained for 3 to 30 days will be randomized (1:1) to intervention group or control group. Both groups receive standard-of-care smoking cessation treatment from the services. The intervention group additionally receives 3-month relapse prevention support via mobile chat messaging, including cessation advice delivered by a live counselor and access to a supportive chatbot via WhatsApp. The control group receives text messaging on generic cessation advice for 3 months as attention control. The primary outcome is tobacco abstinence verified by an exhaled carbon monoxide of
