A 2-arm, single-blind, parallel RCT will be conducted over 12 months. Study invitations will be sent to 600 youth and young adult e-cigarette users and randomized between an intervention arm, which will be using Crush the Crave (n=300), and an assessment-only control arm (n=300) in a 1:1 ratio. The trial protocol is registered with the Center for Open Science (registration digital object identifier: 10.17605/OSF.IO/HMD87). The trial protocol was developed in accordance with the SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) 2013 checklist of recommended items for interventional trials [29].

The study is being conducted by the Ontario Tobacco Research Unit. Approval for the study protocol was obtained from the University of Toronto Office of Research Ethics (protocol number: 00038410).

Eligible participants are youth aged 16 to 29 years who live in Canada and have used nicotine e-cigarettes in the previous 30 days. Study participants will be recruited through the Vaping Dependence Cohort—an existing panel of youth enrolled in a prospective cohort study at the University of Toronto who provided consent for recontact in future studies at the Ontario Tobacco Research Unit. This panel is comprised of a broad sample of youth who self-reported current or past regular use of nicotine e-cigarettes. The use of nicotine e-cigarettes was assessed through a question that asked respondents if they had used e-cigarettes daily, in the past week, in the past month, in the past 3 months, or in the past year and if they had ever used an e-cigarette. This cohort was designed to balance recruitment by smoking status (ever or never), e-cigarette use (ever or never), and age (16-18 years or 19-25 years). Consequently, the prevalence of smoking, e-cigarette use, and younger participants was higher than what would be expected in a simple random sample of the population. An analysis controlling for the study design elements found that the within-group characteristics of the included youth were broadly consistent with expectations, which were based on a representative sample [9].

After eligibility screening, participants must provide informed consent to proceed with study enrollment. The web-based consent form contains information about the study, the Crush the Crave app, participant eligibility, requirements and expectations for study participation, compensation, data collection, and plans for protecting participants and their privacy (ie, data deidentification), as well as the contact information of study staff and the University of Toronto Office of Research Ethics. Those who agree to participate in the study will receive an email containing a link to download the Crush the Crave app (sent to the email addresses they provided).

Each participant in the intervention and control arms will receive compensation (CAD $10 [US $7.46] electronic gift card) upon completion of the baseline survey questionnaire and each time they complete a follow-up survey throughout the course of the study.

Eligible participants will be identified from the Vaping Dependence Cohort. The rand() function in Excel (Microsoft Corporation) allowed for simple randomization; the top 50% highest numbers identified the participants that will receive invitations to use the Crush the Crave app. A research assistant from the Vaping Dependence Cohort will conduct the randomization and create a variable with a blinded key for the initial data analysis, which will allow the investigators and analyst to be blinded to the group allocation up until the data analysis is complete.

A baseline questionnaire will be sent to both the intervention group and the control group, using a self-administered web-based survey. This will collect comprehensive data on the history and characteristics of vaping (eg, vaping dependence, use of e-cigarettes, and self-confidence to quit), self-perceived addiction to vaping, health status (including mental health, mood, and perceived stress), and current and previous history of the use of other substances (combustible cigarettes, marijuana, alcohol, hookahs, and other tobacco products). The baseline survey will also ask questions on environmental factors and cessation goals. Self-reported demographic data (age, sex, gender and sexual orientation, province and country of residence, race and ethnicity, education, and marital status) will also be collected in the baseline survey.

A follow-up survey will be sent to the control and intervention groups at 3, 6, 9, and 12 months. Responses to the follow-up survey will be used to analyze any significant changes in vaping habits and differences between groups. The follow-up survey questionnaire includes items on cross-contamination and the use of cessation methods.

The primary outcome variable will be self-reported 30-day PPA at 3 months, operationalized as not having vaped, even a puff, in the last 30 days. The secondary measures include the intention to quit smoking in the next 6 months (yes or no), number of puffs per vaping session, number of vape sessions per day, and number of sessions in the past 30 days.

The mHealth (mobile health) App Usability Questionnaire [33] will be used to collect data on process measures from the intervention group. The mHealth App Usability Questionnaire collects data on the following three main constructs: ease of use and satisfaction (8 items), system information arrangement (6 items), and usefulness (7 items). Data from app analytics will also be used as process measures for the intervention group, including whether participants downloaded the intervention (yes or no), the frequency of use, the most frequently used features, and user reviews.

Qualitative interviews (n=25) will be conducted with participants in the intervention arm to gain insight on the usability and acceptability of the app. Interviews will be audio recorded and transcribed verbatim, and they will be analyzed in NVivo 12 (QSR International) by using a 6-step approach to thematic analysis, as proposed by Braun and Clarke [34].

This is the first-ever RCT study to evaluate the effectiveness of a smartphone app for supporting youth vaping cessation. The primary aim of our study is to determine the effectiveness of the Crush the Crave app in supporting vaping cessation among youth recruited to the intervention arm via comparison with an assessment-only control group. The primary hypothesis is that participants in the intervention group—those using Crush the Crave—will be more likely to be abstinent at the 6-month follow-up point than participants in the assessment-only control arm.

The Crush the Crave app was developed based on the best available evidence on vaping cessation and an empirical investigation on the effectiveness of an earlier version of the app for smoking cessation [22]. At the time of writing, 4 other clinical trial protocols for evaluating vaping cessation interventions among youth and young adults were registered on ClinicalTrials.gov. Of these, only 1 has been completed; the results are accessible in the published scientific literature and show that the intervention was successful (abstinence success rates of 16% for the intervention group and 8% for the control group) in encouraging young adults to stop vaping through an SMS text messaging program [8]. This study was useful in providing a benchmark for intervention effectiveness [8]. Of the 3 remaining protocols that are actively recruiting participants, 2 aim to evaluate the effectiveness of nicotine replacement therapy for vaping cessation among youth and young adults, and 1 aims to determine the effectiveness of a smartphone app called Goal2QuitVaping. Compared to the target sample size in our study (N=600), that of the Goal2QuitVaping study is relatively small (N=45).

It is important to note the potential limitations in some aspects of the design and implementation of our trial. First, most notably, our trial was designed to include an assessment-only control group. We recognize that other app-based interventions for health are typically compared against other active controls or even other app-based interventions. Our methodology was adopted from the methodology used in the only completed trial (at the time of writing) of a technology-based vaping cessation intervention [8]. Second, our study focuses on evaluating the effectiveness of the intervention among youth and young adults who vape nicotine e-cigarettes. Given the recent rise in cannabis vaping among youth, interventions that focus on cannabis vaping will need to be developed and studied rigorously. Finally, we recognize that the active intervention is publicly available on the Apple and Google app stores and that participants in both trial groups may become aware of this fact during the trial. Cross-contamination measures will be put in place to assess awareness of and engagement with the Crush the Crave app among control group participants.

The findings from our trial will help increase our understanding of the process of vaping cessation among youth and provide evidence on the effectiveness of an app-based intervention in helping young people quit vaping. The trial results will also have implications in the development of current and future approaches to youth vaping cessation.