Contact-tracing mobile phone apps have the potential to play a role in controlling
the spread of COVID-19, but their success hinges on widespread uptake by the public. We
report a study that behaviourally pre-tested COVID Tracker, Ireland’s contact-tracing app,
prior to its launch with a large sample of smartphone users. The study was funded by the
Department of Health and run in co-operation with the app’s developers, NearForm.
Participants were randomised to receive different versions of a trial app. They responded
to an online survey while downloading and using the app on their phones in real
time. The experimental manipulations focused on three broad areas: (i) the level of
privacy assurance provided in the app, (ii) the goal-framing of the purpose of the app and
(iii) the structuring of the exposure notification received by users if they are recorded
as a close contact. Almost one in five participants mentioned privacy concerns in relation
to their likelihood of downloading the app. Including additional assurances regarding the
privacy of users’ data in the app successfully lowered participants’ privacy concerns and
boosted engagement. This finding fed into the final version of the app released in July 2020.
We also found minor beneficial effects of restructuring the exposure notification, but did
not find any significant differences between two different types of goal-framing, other
than a subtle effect on how the exposure notification is interpreted. Overall, our
results demonstrate the value of pre-testing contact-tracing apps from a behavioural
perspective to boost uptake, trust and participation.