INTRODUCTION: E-cigarette use among U.S. youth has declined in recent years. This study examined the effect of exposure to "The Real Cost" Youth E-cigarette Prevention Campaign on e-cigarette initiation among U.S. youth aged 11-18. METHODS: Data were analyzed from the first two waves of a longitudinal evaluation of the campaign (baseline: August-December 2023
follow-up: June-September 2024
analyses: 2025). The analysis included youth who reported never having tried an e-cigarette at baseline and completed the follow-up survey (n = 3,408). An exposure index (range: 0-16) was generated using respondents' self-reported frequency of exposure to each of four campaign advertisements (0 = never
4 = very often). The impact of exposure on e-cigarette initiation was examined at follow-up using a discrete-time survival analysis logistic regression model, controlling for potential confounding variables. The estimated number of youth prevented from initiating e-cigarette use was extrapolated to the national youth population. RESULTS: The odds of reporting e-cigarette initiation at follow-up decreased as exposure to campaign advertisements increased. For every unit increase in the exposure index, there was a 6% reduction in the probability of initiation. The campaign prevented an estimated 444,252 (95% CI: 73,639-814,866) U.S. youth aged 11-18 from initiating e-cigarettes between 2023 and 2024. CONCLUSIONS: Youth with higher exposure to "The Real Cost" E-cigarette Prevention Campaign ads were less likely to initiate e-cigarettes during the study period. These findings indicate that the campaign has contributed to recent declines in e-cigarette use among U.S. youth.