Several data-driven epidemiological approaches that have been proposed or trialed for COVID-19 are justified if implemented through transparent processes that involve oversight, write Michelle M. Mello and C. Jason Wang in this Policy Forum. Though, say the authors, "we question the necessity to conduct contact tracing using cellphone and other private data without users' consent." Around the globe in select countries, a range of innovative uses of personal data from outside the health sector have been undertaken to meet the challenge posed by the novel coronavirus. In this Policy Forum, Mello and Wang ask: "Should these approaches be in wider use?" The ethical issues raised by digital epidemiology center on a core tension: these novel uses of people's data can involve both personal and social harms, but so does failing to harness the enormous power of data to arrest epidemics. Considerations in this debate, say the authors, raise important question for governments, like what is the exit strategy for any approach applied? Also, when it comes to respecting autonomy - asking people for permission to access their personal information (or not) - whether such infringements likely to be effective is an important question, among others. A final question is how to ensure that those involved in epidemiologic analysis of novel data sources are accountable for what they do. "Ordinary presumptions about what kind of data uses are ethically acceptable for governments and companies to pursue may need to flex" in these times, say the authors. "But the key principles guiding decision making remain the same." The authors believe some novel epidemiological approaches described for COVID-19 are justified if implemented with the right parameters. "When the epidemic abates, it will be important to reconsider these approaches in light of what has been learned about their benefits and the public's attitudes toward them, so that we are prepared to deploy cutting-edge methods responsibly during the next epidemic."