Background We examined whether the implementation of electronic cigarette (e-cigarette) policies at the state level (e-cigarette-inclusive smoke-free (ESF) policies, excise taxes on e-cigarettes and raising tobacco legal purchasing age to 21 years (T21)) affected recent upward trends in youth e-cigarette use.

Methods Data were from participants from 34 US states who completed the Youth Risk Behavior Survey (YRBS) state surveys in 2017 and 2019 (n=278 271). States were classified as having or not having ESF policies, any e-cigarette excise tax and T21 policies by 1 January 2019. Participants reported ever, past 30-day and frequent (≥20 days) e-cigarette use; past 30-day combustible cigarette smoking; and age, sex and race/ethnicity. Weighted multivariable logistic regression models assessed whether changes in e-cigarette use over time differed by policy status, adjusting for participants’ demographics and combustible cigarette smoking.

Results Prevalence of ever and past 30-day youth e-cigarette use in states with ESF policies decreased during 2017–2019, while the prevalence of these measures in states without ESF policies increased. States with T21 policies showed non-significant changes in prevalence of ever and past 30-day youth e-cigarette use, whereas states without T21 policies showed significant increases in ever and past 30-day youth e-cigarette use. States with ESF and T21 policies showed slower increases in youth frequent e-cigarette use. E-cigarette excise taxes were not associated with decreasing prevalence of youth e-cigarette use.

Conclusions State-level ESF and T21 policies could be effective for limiting growth of youth e-cigarette use despite an overall national increase. Higher e-cigarette excise tax rates may be needed to effectively reduce youth e-cigarette use.