OBJECTIVE Preventing ventilator-associated pneumonia (VAP) is an important goal for intensive care units (ICUs). We aimed to identify the optimal behavior leverage to improve VAP prevention protocol adherence. DESIGN Mixed-method study using adherence measurements to assess 4 VAP prevention measures and qualitative analysis of semi-structured focus group interviews with frontline healthcare practitioners (HCPs). SETTING The 6 ICUs in the 900-bed University Hospital Zurich in Zurich, Switzerland.Patients and participantsAdherence to VAP prevention measures were assessed in patients with a device for invasive ventilation (ie, endotracheal tube, tracheostomy tube). Participants in focus group interviews included a convenience samples of ICU nurses and physicians. RESULTS Between February 2015 and July 2017, we measured adherence to 4 protocols: bed elevation showed adherence at 27% (95% confidence intervals [CI], 23%-31%); oral care at 41% (95% CI, 36%-45%); sedation interruption at 81% (95% CI, 74%-85%); and subglottic suctioning at 88% (95% CI, 83%-92%). Interviews were analyzed first inductively according a grounded theory approach then deductively against the behavior change wheel (BCW) framework. Main behavioral facilitators belonged to the BCW component 'reflective motivation' (ie, perceived seriousness of VAP and self-efficacy to prevent VAP). The main barriers belonged to 'physical capability' (ie, lack of equipment and staffing and side-effects of prevention measures). Furthermore, 2 primarily technical approaches (ie, 'restructuring environment' and 'enabling HCP') emerged as means to overcome these barriers. CONCLUSIONS Our findings suggest that technical, rather than education-based, solutions should be promoted to improve VAP prevention. This theory-informed mixed-method approach is an effective means of guiding infection prevention efforts. Abstract Objective: Preventing ventilator-associated pneumonia (VAP) is an important goal for intensive care units (ICUs). We aimed to identify the optimal behavior leverage to improve VAP prevention protocol adherence. Design: Mixed-method study using adherence measurements to assess 4 VAP prevention measures and qualitative analysis of semi-structured focus group interviews with frontline healthcare practitioners (HCPs). Setting: The 6 ICUs in the 900-bed University Hospital Zurich in Zurich, Switzerland. Patients and participants: Adherence to VAP prevention measures were assessed in patients with a device for invasive ventilation (ie, endotracheal tube, tracheostomy tube). Participants in focus group interviews included a convenience samples of ICU nurses and physicians. Results: Between February 2015 and July 2017, we measured adherence to 4 protocols: bed elevation showed adherence at 27% (95% confidence intervals [CI], 23%-31%); oral care at 41% (95% CI, 36%-45%); sedation interruption at 81% (95% CI, 74%-85%); and subglottic suctioning at 88% (95% CI, 83%-92%). Interviews were analyzed first inductively according a grounded theory approach then de...