Young adults (18–30 years) comprise most U.S. waterpipe tobacco smokers (Kasza et al., 2017, Robinson et al., 2018), with 11% reporting past 30-day use (Robinson et al., 2018) and >25% who have never smoked waterpipe tobacco susceptible to initiation (i.e., open to trying waterpipe tobacco) (Mays et al., 2016). Young adults initiate and sustain waterpipe tobacco smoking (WTS) due to factors including appealing flavors, the social nature of WTS, and misperceptions that WTS is not harmful or addictive (Akl et al., 2015, Lipkus and Mays, 2018, Lipkus et al., 2017, Villanti et al., 2017, Villanti et al., 2019, 2019). However, WTS exposes young people to harmful toxicants and increases risks of negative health outcomes, nicotine addiction, and subsequently smoking cigarettes (Al Oweini, Jawad, & Akl, 2019). Interventions are needed to prevent and reduce WTS in young adults.

The U.S. Food and Drug Administration (FDA) can use public education media campaigns to address young adults’ WTS as they have with cigarettes (Kranzler and Hornik, 2019, MacMonegle et al., 2018) and e-cigarettes (U.S. Food & Drug Administration, 2021), but there is limited research on WTS messaging to guide campaigns. Studies have investigated messages for warning labels and point-of-sale communication for WTS (Cornacchione Ross et al., 2019, Islam et al., 2016, King et al., 2019, Maziak et al., 2019, Sutfin et al., 2019). Messages about risks of health harms and addiction can decrease intentions to smoke in susceptible never smokers, increase motivation to quit in those who smoke, and increase risk perceptions (Johnson and Mays, 2021, Lipkus and Mays, 2018, Mays et al., 2016, Mays et al., 2020). However, studies testing messages in those who have never smoked but are susceptible are limited (Lipkus & Mays, 2017), and others tested messages as part of cessation interventions for those who currently smoke (Mays et al., 2021).

Media campaigns are an evidence-based intervention for preventing and reducing tobacco use (Centers for Disease Control and Prevention, 2014, Centers for Disease Control and Prevention, 2014, MacMonegle et al., 2018, Shrestha et al., 2021, Office Of the U.S. Surgeon General, 2004) and, in the past, have relied primarily on television (Centers for Disease Control and Prevention, 2014, Centers for Disease Control and Prevention, 2014). Recent campaigns have shifted to digital media (e.g., mobile, social media) (Crankshaw et al., 2021, Crankshaw et al., 2022, Guillory et al., 2021) due to the potential for high reach in populations such as young adults (Ilakkuvan et al., 2019, Villanti et al., 2017). As campaigns shift from traditional to digital media, the amount of message exposure (i.e., dose, or how many times a person should see campaign messages) needed to achieve intended effects is an important consideration. Decisions about message dose are usually determined in the media buying process based on recommendations using gross ratings points, or the percent of the audience reached multiplied by the number of times they are exposed to the message (Centers for Disease Control and Prevention, 2014, Centers for Disease Control and Prevention, 2014). Public health agencies provide recommendations for campaign dose using traditional media (Centers for Disease Control and Prevention, 2014, Centers for Disease Control and Prevention, 2014), and outcomes are improved (e.g., higher smoking quit attempts) when campaigns achieve adequate dose through repeated message exposure (Durkin et al., 2012, Farrelly et al., 2005, Farrelly et al., 2011, Farrelly et al., 2012, Hyland et al., 2006, McAfee et al., 2013, Wakefield et al., 2011). One recent study tested the effects of a campaign communicating chemical constituents in WTS to youth and young adults at the point-of-sale (e.g., convenience stores) (Sutfin et al., 2021), finding limited effects on target outcomes. The researchers attributed this to the low observed dose of exposure, highlighting the importance of additional research on dose of exposure for WTS messaging (Sutfin et al., 2021).

Recent FDA tobacco campaigns have relied heavily on digital media but had limited impact on intended outcomes (Crankshaw et al., 2021, Crankshaw et al., 2022, Guillory et al., 2021). Discussions about these limited effects have focused on message dose, specifically the lack of evidence to inform decisions about message dose for digital media (Crankshaw et al., 2021, Crankshaw et al., 2022, Guillory et al., 2021). Examining how the dose of message exposure for WTS and other tobacco-related messages affects intended outcomes can inform future campaign implementation decisions. This randomized trial addressed gaps in the WTS intervention research by examining the effects of WTS messaging among young adults who never smoked waterpipe tobacco and were susceptible or reported current WTS and by exploring message dose effects. We hypothesized that exposure to intervention messages would decrease WTS initiation among susceptible never smokers and increase cessation in those who smoked.