IntroductionBehaviour change is key to the public health measures that have been issued in many countries worldwide to contain COVID-19. Public health measures will only take preventive effect if people adhere to them. Interventions taking health psychology approaches may promote adherence to public health measures. However, evidence from randomised controlled behaviour change trials is scarce during an ongoing pandemic. We aim to use the example of hand washing with soap to optimise and test a digital, theory-based and evidence-based behaviour change intervention to prevent the spread of COVID-19.Methods and analysisThis protocol describes the multiphase optimisation strategy for the preparation, optimisation and evaluation of a theory-based and evidence-based intervention delivered via app. The app aims to promote correct hand hygiene at key times in the adult general population. The study will be conducted in German-speaking Switzerland. The preparation phase has identified relevant behavioural determinants of hand hygiene during a pandemic from health behaviour theories and formative research with focus groups (n=8). The optimisation phase will identify the most effective and acceptable combination and sequence of three intervention modules in a parallel randomised trial (n=387) with analysis of variance (ANOVA) and regression analysis. Additionally, thematic analysis of qualitative interview data (n=15) will be used to gain insights on the feasibility, usability and satisfaction of the intervention. The evaluation phase will test the optimised intervention against an active control group in a randomised controlled trial (n=205), analysing pre-post differences and 6-month follow-up effects with ANOVA and regression analysis.Ethics and disseminationThe trial was approved by the Cantonal Ethics Commission Bern of the Swiss Association of Research Ethics Committees (protocol ID: 2021-00164). Final results will be presented in peer-reviewed journals and at conferences.Trial registration numberNCT04830761.

Background Hand hygiene is an effective behavior for preventing the spread of the respiratory disease COVID-19 and was included in public health guidelines worldwide. Behavior change interventions addressing hand hygiene have the potential to support the adherence to public health recommendations and, thereby, prevent the spread of COVID-19. However, randomized trials are largely absent during a pandemic; therefore, there is little knowledge about the most effective strategies to promote hand hygiene during an ongoing pandemic. This study addresses this gap by presenting the results of the optimization phase of a Multiphase Optimization Strategy of Soapp, a smartphone app for promoting hand hygiene in the context of the COVID-19 pandemic. Objective This study aimed to identify the most effective combination and sequence of 3 theory- and evidence-based intervention modules (habit, motivation, and social norms) for promoting hand hygiene. To this end, 9 versions of Soapp were developed (conditions), and 2 optimization criteria were defined: the condition with the largest increase in hand hygiene at follow-up and condition with the highest engagement, usability, and satisfaction based on quantitative and qualitative analyses. Methods This study was a parallel randomized trial with 9 intervention conditions defined by the combination of 2 intervention modules and their sequence. The trial was conducted from March to August 2021 with interested participants from the Swiss general population (N=232; randomized). Randomization was performed using Qualtrics (Qualtrics International Inc), and blinding was ensured. The duration of the intervention was 34 days. The primary outcome was self-reported hand hygiene at follow-up, which was assessed using an electronic diary. The secondary outcomes were user engagement, usability, and satisfaction assessed at follow-up. Nine participants were further invited to participate in semistructured exit interviews. A set of ANOVAs was performed to test the main hypotheses, whereas a thematic analysis was performed to analyze the qualitative data. Results The results showed a significant increase in hand hygiene over time across all conditions. There was no interaction effect between time and intervention condition. Similarly, no between-group differences in engagement, usability, and satisfaction emerged. Seven themes (eg, “variety and timeliness of the task load” and “social interaction”) were found in the thematic analysis. Conclusions The effectiveness of Soapp in promoting hand hygiene laid the foundation for the next evaluation phase of the app. More generally, the study supported the value of digital interventions in pandemic contexts. The findings showed no differential effect of intervention conditions involving different combinations and sequences of the habit, motivation, and social norms modules on hand hygiene, engagement, usability, and satisfaction. In the absence of quantitative differences, we relied on the results from the thematic analysis to select the best version of Soapp for the evaluation phase. Trial Registration ClinicalTrials.gov NCT04830761; https://clinicaltrials.gov/ct2/show/NCT04830761 International Registered Report Identifier (IRRID) RR2-10.1136/bmjopen-2021-055971

BACKGROUND Hand hygiene is an effective behavior for preventing the spread of the respiratory disease COVID-19, and was included in public health guidelines worldwide. Behavior change interventions addressing hand hygiene have the potential to support the adherence to public health recommendations and thereby prevent the spread of COVID-19. However, randomized trials during a pandemic are largely absent, wherefore there is little knowledge about the most effective strategies to promote hand hygiene during an ongoing pandemic. The present study addresses this gap by presenting the results of the optimization phase of a Multiphase Optimization Strategy of Soapp, a smartphone app to promote hand hygiene in the context of the COVID-19 pandemic. OBJECTIVE The goal was to identify the most effective combination and sequence of three theory- and evidence-based intervention modules (Habit, Motivation, Social Norms) to promote hand hygiene. To this aim, nine versions of Soapp were developed (conditions) and two optimization criteria were defined: i) condition with largest increase in hand hygiene at follow-up and ii) condition with highest engagement, usability and satisfaction based on quantitative and qualitative analyses. METHODS The study design was a parallel randomized trial with nine intervention conditions defined by the combination of two intervention modules and their sequence. The trial was conducted from March to August 2021 with interested participants of the Swiss general population (N = 232 randomized). Randomization was performed by Qualtrics and blinding was ensured. The duration of the intervention was 34 days. The primary outcome was self-reported hand hygiene at follow-up, assessed via an electronic diary. Secondary outcomes were user engagement, usability and satisfaction, assessed at follow-up. Participants were further invited for semi-structured exit interviews (n = 9). A set of Anovas was performed to test the main hypotheses while thematic analysis was performed to analyze the qualitative data. RESULTS Results showed a significant increase in hand hygiene over time across all conditions. There was no interaction effect of time and intervention condition. Likewise, no between-group difference in engagement, usability and satisfaction emerged. Seven themes (e.g., “variety and timeliness of the workload”, “social interaction”) were found in the thematic analysis. CONCLUSIONS The current findings evidenced no effect of intervention condition of a habit, motivation and social norms module on hand hygiene, engagement, usability and satisfaction. In the absence of quantitative differences, we relied on the results from the thematic analysis to select the best version of Soapp for the evaluation phase. CLINICALTRIAL NCT04830761 INTERNATIONAL REGISTERED REPORT RR2-10.1136/bmjopen-2021-055971