Epidemiology of digital contact tracing: lessons learned and future perspectives

ABSTRACT
Digital contact tracing is a new public health tool developed and deployed worldwide during the COVID-19 pandemic. Contact-tracing apps measure proximity and duration of close contacts, allowing individuals who had risky exposures to be rapidly notified when cases are confirmed. Here we summarise the main insights we have obtained from the NHS COVID-19 app used in England and Wales. Beyond its epidemiological impact as a public health intervention the app revealed individual and population determinants of transmissions. The app’s capabilities for precision epidemic surveillance at scale also offered unprecedented and near-real-time insights into epidemic dynamics, giving early indications of changes in the reproduction number Rt and their drivers. Finally, we present our perspective for the future of digital tools for epidemic preparedness.