[On the ethics of corona apps].

Definition of the problem: In spring 2020, as much of the world was emerging from widespread "lockdowns" as an emergency measure to combat the spread of SARS-CoV‑2, there was sustained discussion about how to lift measures while preventing further waves of the virus and the need for further lockdowns. One strategy that attracted significant attention was the use of digital contact-tracing apps to quickly alert users of possible exposure to the virus, and to direct them into quarantine. The initially high expectations placed upon this strategy were not met-despite the implementation of a digital contact-tracing app in Germany, further restrictions have been placed on the general population in response to further waves of the virus. We consider how digital contact tracing might have been made more effective. Arguments: We argue that there is a conflict between collecting as little data as possible, and more effective epidemic control. In contrast to the "Corona-Warn-App" that was implemented in Germany, an app that stored more information on a central server (a so-called "centralized" app) had the potential to significantly decrease viral spread. We then look at the privacy-based arguments against the centralized storage of information, suggesting that "decentralized" systems have privacy problems of their own. Results: The German debate on digital contact tracing apps was quickly dominated by privacy concerns, to the detriment of other ethical factors such as enhancing potential effectiveness. Furthermore, the potential problems with privacy inherent in decentralized apps were obscured in the discussion. Once we recognize these two aspects, we can see that there is an argument to be made for preferring centralized digital contact-tracing apps.