The paper Wearable Proximity Sensors for Monitoring a Mass Casualty Incident Exercise: Feasibility Study has just been published by the Journal of Medical Internet Research! In this study, we aimed to assess the feasibility of using wearable proximity sensors to measure proximity events during a Mass Casualty Incidence (MCI) simulation. We measured the interactions between 238 participants involved in the exercise, including 14 medical doctors, 16 nurses, 134 victims, and 27 health care assistants. Data collected in such a way allowed to evaluate the performance of the medical staff during the exercise and the potential presence of bottlenecks for the hospital rooms where victims were examined by doctors. Our study represents the first example of unsupervised data collection of face-to-face contacts during an MCI exercise by means of wearable proximity sensors.