BackgroundThere is mixed evidence on the effectiveness of vaccination-related interventions. A major limitation of most intervention studies is that they do not apply randomized controlled trials (RCTs), the method that, over the last 2 decades, has increasingly been considered as the only method to provide proof of the effectiveness of an intervention and, consequently, as the most important instrument in deciding whether to adopt an intervention or not. This study, however, holds that methods other than RCTs also can produce meaningful results.ObjectiveThe aim of this study was to evaluate 2 mobile phone–based interventions aimed at increasing parents’ knowledge of the measles-mumps-rubella (MMR) vaccination (through elements of gamification) and their psychological empowerment (through the use of narratives), respectively. The 2 interventions were part of an RCT.MethodsWe conducted 2 studies with the RCT participants: a Web-based survey aimed at assessing their rating of the tool regarding a number of qualities such as usability and usefulness (N=140), and qualitative telephonic interviews to explore participants’ experiences with the app (N=60).ResultsThe results of the survey showed that participants receiving the knowledge intervention (alone or together with the empowerment intervention) liked the app significantly better compared with the group that only received the empowerment intervention (F2,137=15.335; P<.001). Parents who were exposed to the empowerment intervention complained that they did not receive useful information but were only invited to make an informed, autonomous MMR vaccination decision.ConclusionsThe results suggest that efforts to empower patients should always be accompanied by the provision of factual information. Using a narrative format that promotes parents’ identification can be an appropriate strategy, but it should be employed together with the presentation of more points of views and notions regarding, for instance, the risks and benefits of the vaccination at the same time.Trial RegistrationInternational Standard Randomized Controlled Trial Number 30768813; http://www.isrctn.com/ ISRCTN30768813 (Archived by WebCite at http://www.webcitation.org/6xOQSJ3w8)