Background <p>Adolescent vaping prevalence in the U.S. surged dramatically from 2017 to 2019, then declined significantly, making 2019 an inflection point. Anti-vaping advertising and media reporting on e-cigarette or vaping use-associated lung injury (EVALI) may have contributed to the decline. This study examined whether anti-vaping advertising exposure and EVALI awareness were associated with adolescents’ quit attempts, intentions to quit, and susceptibility to future vaping.</p> Methods <p>Data from the 2017–2018 (<i>N</i> = 117 757) and 2019–2020 (<i>N</i> = 143 565) California Student Tobacco Survey were analyzed. Participants’ quit attempts, intentions to quit, and susceptibility to future vaping in the two periods were compared. Multivariable logistic regressions were used to examine the effects of anti-vaping advertising exposure and EVALI awareness on these three dimensions.</p> Results <p>Compared to 2017–2018, middle and high school students who currently vaped in 2019–2020 had higher rates of quit attempts (53.2% vs. 28.8%, <i>p</i> &lt; 0.001) and intentions to quit (79.1% vs. 56.9%, <i>p</i> &lt; 0.001). Susceptibility to future vaping among those who never vaped was lower in 2019–2020 than in 2017–2018 (25.7% vs. 30.3%, <i>p</i> &lt; 0.001). Exposure to anti-vaping advertising and awareness of EVALI were significantly associated with higher rates of attempting quitting and intentions to quit. EVALI awareness was negatively associated with susceptibility to future vaping.</p> Conclusions <p>EVALI awareness and exposure to anti-vaping advertising were associated with positive changes in adolescents’ vaping-related attitudes and behavior. A substantial increase in quitting activity among those currently vaping and a decrease in susceptibility to future vaping among those who never vaped likely contributed to the decline in adolescent vaping prevalence since 2019. Future interventions should leverage paid and earned media to facilitate a continued decline in youth tobacco use.</p>