In the workgroup infection epidemiology, projects from the fields pediatric infection epidemiology and modeling are located. We obtain data from secondary sources, such as hospitals and registers or independently established-cohorts. The projects of pediatric infection epidemiology aim at identifying risk factors for the development of asthma and other allergic diseases. Furthermore, we address the use of antibiotics in hospitals and the state of immunosuppression after liver transplantation. Through modeling, we investigate critical factors of temporal processes in infections, transmission paths in hospitals, and graft repulsion reactions. Our conclusions can be used by political decision makers.