Evaluating the reach and engagement of three anti-vaping messages among young Australian adults aged 18-34 through a social media campaign.

Two social media intervention messages will address the environmental risks associated with vaping and anti-vape industry sentiments. From an environmental perspective, the intervention will highlight that disposable vapes are difficult to recycle and, therefore, harmful to the environment. Regarding the anti-vape industry perspective, the intervention will stress that vape companies exploit the hard-earned money of young adults, which could be spent more wisely. The A/B/C testing algorithm will be set to ensure the participants are evenly split in numbers by using the same advertisement costs for each and to ensure that only one of the three messages is 'pushed' to each participant's account. Therefore, the A/B/C testing is equivalent to randomisation and allocation concealment in a randomised design. The campaign will span three months, and participants will receive a unique message from one of three ads at least once per day on their Facebook feed for the duration of the campaign. If there is no observed reach and engagement for a one-week period, we will cease data collection even if the three-month campaign period is not yet completed. In this design, each participant will only be able to see one message on their Facebook feed. However, we cannot control which vape messages participants view, nor can we restrict the audiences from being exposed to a different vape message shared by their peers, different from the one to which they were originally randomised. Each message will include a static text message with emojis and an image. To monitor or assess adherence to interventions, data from Meta backend will be collected.