  To help curb the spread of the COVID-19 pandemic, governments and public
health authorities around the world have launched a number of contact-tracing
apps. Although contact tracing apps have received extensive attentions from the
research community, no existing work has characterized the users' adoption of
contact tracing apps from the app market level. In this work, we perform the
first market-level analysis of contact tracing apps. We perform a longitudinal
empirical study (over 4 months) of eight government-backed COVID-19 contact
tracing apps in iOS app store. We first collect all the daily meta information
(e.g., app updates, app rating, app comments, etc.) of these contact tracing
apps from their launch to 2020-07-31. Then we characterize them from release
practice, app popularity, and mobile users' feedback. Our study reveals various
issues related to contact tracing apps from the users' perspective, hoping to
help improve the quality of contact tracing apps and thus achieving a high
level of adoption in the population.
