In this chapter, the Corona-Warn-App (CWA), a digital contact tracing tool developed during the SARS-CoV-2 pandemic, will be outlined as an example of a digital tool supporting Essential Public Health Operation (EPHO) 2. The CWA was the official contact tracing app in Germany, commissioned by the Robert Koch Institute, developed by SAP, and run on infrastructure set up by T-Systems. During the first months of the pandemic, decision-makers feared that manual contact tracing would not be sufficient to end infection chains. It turned out that with digital contact tracing, a slight paradigm shift—from tracing contact persons to tracing contact—was established. This, in turn, changes the vantage point for future measures in monitoring and response to health hazards and emergencies. Germany’s contact tracing app had a very high uptake in the German population. The decision to follow a data-protection-friendly path was warmly welcomed by the German civil society and might have had an impact on the positive opinion towards the app, thus helping to improve its efficacy. The Corona-Warn-App followed three main aims: (1) Provide test results (quickly), (2) warn other users (by sharing), and (3) determine potential risks (correctly). Despite the limitations of its underlying technology, the Corona-Warn-App has shown to be an effective digital tool which has probably helped to reduce the number of infected persons and deaths during the SARS-CoV-2 pandemic.