  By using modern cryptographic techniques, privacy-preserving Automated
Exposure Notification (AEN) technologies offer the promise of mitigating
disease spread by automatically recording contacts between people over the
incubation period while maintaining individual data privacy. Today, public
health departments in States and other countries around the world are deploying
AEN systems at a rapid pace. Though many organizations conducted research prior
to deploying apps, experience around the world shows that contact-tracing apps
are installed and used at relatively low levels. This whitepaper is intended to
provide usable information for States who are considering the deployment of an
AEN system, as well as to guide ongoing improvements for States that have
already deployed. We outline the human factors considerations related to
employing AEN systems with the ultimate goal of controlling the spread of
COVID-19, including the GAEN consortium Exposure Notifications (EN) Express
tool. We will also provide a practical design and implementation guide for
States and others designing and deploying AEN systems, as well as a set of
recommendations for assessing deployment of contact tracing apps and targeting
areas of concern to improve efficacy of use during and after initial
deployment. As a case study, we consider the commercial app deployed by the
state of Pennsylvania (PA) and the ongoing efforts to drive user adoption
there.
