This research project aimed to safely reduce antibiotic prescriptions in children under five suspected of a lower respiratory tract infection (RTI) at the emergency department (ED), by implementing a clinical decision rule.DesignIn a stepped-wedge, cluster randomized trial we included children aged one month to five years presenting with fever and cough or dyspnoea to eight EDs in the Netherlands . In the pre-intervention phase children received usual care. During the intervention phase a validated clinical prediction model (Feverkidstool) including clinical characteristics and C-reactive protein was implemented as a decision rule guiding antibiotic prescription. We obtained data of 999 children (61% male, median age 17 months (IQR 9 to 30)) between January 1, 2016 and September 30, 2018; 402 during the intervention phase. Data include general and clinical characteristics, interventions (diagnostic tests, hospitalisation), and for a subset of patients microbiological data are available