AI-generated smoking prevention videos on Instagram achieve greater reach when short-term consequences are addressed

Background Tobacco use is a major preventable cause of cancer, and social media offers scalable opportunities for prevention. AI-generated virtual influencers may reduce production costs, but the effects of message framing on campaign delivery remain unclear. Objective The objective was to compare AI-generated smoking prevention videos emphasising long-term cancer consequences versus short-term consequences under real-world conditions on Instagram. Methods Ten Instagram Reels featuring the same AI-generated character were deployed in a controlled field experiment, with five videos emphasising short-term consequences of smoking and five videos emphasising long-term consequences of smoking. Budget, campaign duration, and targeting were held constant, with each video treated as an independent unit of analysis. Outcomes included reach, cost per 1,000 accounts reached, link clicks, cost per link click, interactions, and cost per interaction. Conditions were compared using exact Mann-Whitney U tests with Holm adjustment and exact permutation tests for sensitivity analyses. Results Videos emphasising short-term consequences of smoking achieved greater reach than videos with long-term cancer framing (median 14,117 vs 11,820; Holm-adjusted p =.048) and lower cost per 1,000 accounts reached (€3.15 vs €3.86; Holm-adjusted p =.048). No significant differences were found for link clicks, cost per link click, interactions, or cost per interaction. Conclusions In this prevention campaign, short-term framing of smoking-related adverse effects was associated with broader and less costly platform-mediated distribution, but with similar engagement. Future research should examine whether increased reach translates into meaningful cancer prevention outcomes.