The COVID-19 pandemic has prompted countries around the world to introduce smartphone apps to support disease control efforts. Their purposes range from digital contact tracing to quarantine enforcement to vaccination passports, and their effectiveness often depends on widespread adoption. While previous work has identified factors that promote or hinder adoption, it has typically examined data collected at a single point in time or focused exclusively on digital contact tracing apps. In this work, we conduct the first representative study that examines changes in people's attitudes towards COVID-19-related smartphone apps for five different purposes over the first 1.5 years of the pandemic. In three survey rounds conducted between Summer 2020 and Summer 2021 in the United States and Germany, with approximately 1,000 participants per round and country, we investigate people's willingness to use such apps, their perceived utility, and people's attitudes towards them in different stages of the pandemic. Our results indicate that privacy is a consistent concern for participants, even in a public health crisis, and the collection of identity-related data significantly decreases acceptance of COVID-19 apps. Trust in authorities is essential to increase confidence in government-backed apps and foster citizens' willingness to contribute to crisis management. There is a need for continuous communication with app users to emphasize the benefits of health crisis apps both for individuals and society, thus counteracting decreasing willingness to use them and perceived usefulness as the pandemic evolves.

翻译：COVID-19疫情促使世界各国推出智能手机应用以支持疾病防控工作。这些应用的功能涵盖数字接触追踪、隔离管控及疫苗接种护照等多个领域，其有效性往往取决于广泛采用程度。虽然已有研究识别出促进或阻碍应用采纳的因素，但通常基于单次时间点的数据采集，或仅聚焦于数字接触追踪类应用。本研究首次开展了具有代表性的纵向调研，追踪疫情暴发前1.5年内民众对五类COVID-19相关智能手机应用的态度变迁。我们于2020年夏至2021年夏期间在美国和德国进行了三轮调查（每轮每国约1000名参与者），考察了人们在疫情不同阶段的使用意愿、感知效用及态度倾向。结果表明：即使在公共卫生危机中，参与者始终将隐私视为核心关切，而身份关联数据的收集会显著降低COVID-19应用的接受度。对权威机构的信任是提升政府支持应用可信度、增强公民参与危机管理意愿的关键要素。需持续与应用用户沟通，强调健康危机应用对个人与社会的双重价值，以此抵消随着疫情演变而持续走低的使用意愿与感知效用。