Book excerpt: Aside from the dramatic effects that the COVID-19 pandemic has had on the lives of people everywhere, it has also triggered and accelerated some important process changes in healthcare. Digital health has become ever more important, supporting test strategies and contact tracing, statistical analysis, prognostic modeling, and vaccination roll-out and documentation. Video calls have become more common, and it seems likely that all these changes will continue to influence healthcare in the longer-term. This book presents the proceedings of dHealth 2021 – the 15th annual conference on Health Informatics Meets Digital Health – held as a virtual conference on 11 & 12 May 2021. The dHealth conference is where research and application meet as equals, and the conference series has been contributing to scientific exchange and networking since 2007. The 2021 edition is the second that has been organized virtually. Each year, this event attracts 300+ participants from academia, industry, government and healthcare organizations, and provides a platform for researchers, practitioners, decision makers and vendors to discuss innovative health informatics and dHealth solutions with the aim of improving the quality and efficiency of healthcare. The 24 papers included here offer an insight into the research on digital health conducted during the COVID-19 crisis, and topics include the management of infectious diseases, telehealth services, standardization and interoperability in healthcare, nursing informatics, data analytics, predictive modeling and digital tools for rare-disease research. The book provides new healthcare insights from both science and practice, and will be of interest to all those working in healthcare.