COVID-19 contact-tracing smartphone application usage-The New Zealand COVID Tracer experience.

Contact tracing has been a central pillar of the nonpharmaceutical health system response to the COVID-19 pandemic. Countries around the world have devoted unprecedented levels of resources to build up their testing and tracing capabilities, including the development and deployment of smartphone-based applications. Yet despite these nontrivial investments, the body of academic literature evaluating the effects of the smartphone-based applications remains scant and many apps have not delivered the promised benefits (Bano et al.