Impact of Privacy Messaging on COVID-19 Exposure Notification App Downloads: Evidence From a Randomized Experiment

INTRODUCTION: Digital contact-tracing smartphone apps have the potential to slow the spread of disease but are not widely used. We tested whether messages describing how a COVID-19 digital contact-tracing app protects users’ privacy led to increased or decreased intentions to download the app by either calming privacy concerns or increasing their saliency. DESIGN: Randomized controlled trial. SETTING/PARTICIPANTS: We recruited adult smartphone owners in the U.S. (oversampled for younger adults aged 18–34 years) in November 2020 through an online panel. INTERVENTION: Survey software randomly assigned 860 participants to 1 of 2 parallel messaging conditions (n=430 privacy assured, n=430 no privacy described). MAIN OUTCOME MEASURES: 4-point scale of intention to use the app “if public health officials released a COVID Exposure Notification app in their state” that averaged likelihood to (1) download and install the app on their phone; (2) keep the app active on their phone; and (3) keep Bluetooth active on their phone (needed for the app to work). RESULTS: After removing incompletes, those who failed the manipulation checks, or those who had already downloaded a COVID-19 digital contact-tracing app, we analyzed 671 participants (n=330 privacy, n=341 no privacy) in 2021. There was no relationship between privacy condition and download intention (mean(privacy)=2.69, mean(noprivacy)=2.69, b=0.01, 95% CI= –0.13, 0.15, p=0.922) but also no evidence that describing the app's security increased context-dependent privacy concerns (measured 3 ways). Instead, we found increased endorsement of data security in the privacy condition using a scale of beliefs about the app keeping privacy secure (mean(privacy)=2.74, mean(noprivacy)=2.58, b=0.16, 95% CI=0.04, 0.28, p=0.009, small effect ω(2)=0.009). CONCLUSIONS: This study provides some evidence that people developing contact-tracing messaging campaigns do not need to worry that describing a digital contact-tracing app's privacy protections will backfire. Future mixed methods testing of messages about who has access to information—and for how long—may uncover new communication strategies to increase public trust in contact-tracing apps. TRIAL REGISTRATION: This study is registered with AsPredicted#51826