**2. Materials and Methods**

#### *2.1. Design and Setting*

All dialysis clinics belonging to the Fresenius Medical Care (FMC) European Nephrocare Network confer clinical data to a centralized data-repository, namely the European Clinical Database (EuCliD®, Fresenius Medical Care, Deutschland GmbH, Vaiano Cremasco, Italy) [22,23]. Since April 2020, all SARS-CoV-2 infections (suspected and confirmed cases as well as initial symptoms), diagnostic procedures, and clinical endpoints are reported in the treatment incident report (TIR) module in EuCLiD®. We used aggregated data abstracted from the TIR, open source data describing epidemic dynamics in European countries, as well as aggregated data on biochemical assays prescriptions and results to estimate outbreak risk in dialysis clinics belonging to the FMC European Nephrocare Network.
