Best Practice Guidance for Digital Contact Tracing Apps: A Cross-disciplinary Review of the Literature (Preprint)

Abstract

BACKGROUND Digital contact tracing apps (DCTAs) have the potential to augment contact tracing systems and disrupt Coronavirus 2019 (COVID-19) transmission. Despite many countries deploying DCTAs, few have disrupted COVID-19 transmission sufficiently to avoid the most restrictive social distancing measures. OBJECTIVE Our aim was to describe and provide best practice guidance on the design considerations of the ideal digital contact tracing app (IDCTA). METHODS We identified key considerations from the literature and used a cross disciplinary approach to develop best practice guidance for the development of the IDCTA. We conducted a search of the indexed and grey literature to identify articles describing or evaluating DCTAs. We searched Ovid Medline using a combination of free text terms and MeSH search terms. We performed a search of the grey literature using the World Health Organisation (WHO) Institutional Repository for Information Sharing, the European Centre for Disease Control (ECDC) publications library and Google, including the websites of many health protection authorities. Articles which were acceptable for inclusion in our evidence synthesis were peer-reviewed publications cohort studies, randomised trials, modelling studies, technical reports, white papers and media reports which related to digital contact tracing. RESULTS Ethical, user experience, privacy and data protection, technical, clinical, societal and evaluation considerations were identified from the literature. The IDCTA should be voluntary and should be equitably available and accessible. Therefore. the IDCTA should be disseminated, free of charge and free smart-phones or monofunctional digital contact tracing devices should be deployed in parallel to groups who may not otherwise have access to DCTAs. The IDCTA interface elements should enable multi-modal interaction (e.g., supported by voice control), with comprehensive contents that are available in different languages. Dynamic, consistently updated information on confirmed cases, testing sites, vaccination sites, current government restrictions and state preventive strategies could enhance user engagement. The IDCTA should be adherent to data protection regulation and follow the principles of privacy by design. Bluetooth LE is recommended for DCTA contact event detection but combining it with ultrasound technology may improve DCTA accuracy without significant compromises on privacy preservation and availability. A decentralised privacy preserving protocol should be followed to enable DCTA users exchange and record temporary contact numbers during contact events. The IDCTA should define and risk stratify contact events according to proximity, duration of contact and the infectiousness of the case at the time of contact. Function creep should be prevented by defining at the outset the limits of the DCTA. Defining from DCTA lauch how its effectiveness will be evaluated is important from an ethical point of view. CONCLUSIONS In conclusion, we identified from the literature key considerations when developing the IDCTA and provide a best practice approach to these considerations.