Short report: Who does or does not use the "Corona-Warn-App" and why?

To slow the spread of SARS-CoV-2, the German government released the "Corona-Warn-App", a smartphone application that warns users if they have come into contact with other users tested positive for SARS-CoV-2. Since using the "Corona-Warn-App" is health-relevant behavior, it is essential to understand who is (and who is not) using it and why. In N = 1,972 German adults, we found that non-users were on average older, female, healthier, in training, and had low general trust in others. The most frequently named reasons by non-users were privacy concerns, doubts about the effectiveness of the app, and lack of technical equipment.