Burden of infectious diseases in children during the first year after solid organ transplantation.

Infections are a leading cause of morbidity and mortality in pediatric solid organ transplant recipients (SOT). Comprehensive data in this population is limited. We included pediatric SOT from the Swiss national cohort aged 0-18 years prospectively from 2008 to 2022. Using standardized definitions, all clinically relevant infections during the first year after transplant were analyzed. Associations with age, organ type, and rejection episodes were assessed. A total of 285 pediatric SOT were included, with kidney (41%) and liver (37%) transplants being the most common. During the first-year post-transplant, 53% (151/285) of patients experienced at least one infection, totaling 360. The overall incidence was 1.36 infection/person/year. Viral infections predominated (53%), followed by bacterial (41%) and fungal infections (6%). Patients receiving liver and lung transplants had higher infection rates (1.91 and 2.53 per person-year, respectively). In multivariate analysis type of transplant and male sex remained associated with increased risk of infection. Viral infections were overrepresented in younger recipients, while bacterial infections were most frequent in the first 3 months post-transplant. Pediatric SOT recipients face a substantial burden of infection. This underscores the need for specific prevention, early recognition, and coordinated management strategies to reduce infection-related morbidity.