Use and effectiveness of Digital Contact Tracing during COVID-19 pandemic: a systematic review

Background Contact tracing (CT) is a pillar of infection control during outbreaks and its implementation has been great ally in the context of the COVID-19 pandemic that pressured national health systems. Digital CT (DCT) aids manual CT by logging proximity contacts and timely notifying contacts of positive cases, contributing to greater epidemic. We aim to systematically review and critically appraise the available evidence on adoption, effectiveness, acceptance and barriers to access of available CT apps. Methods We conducted a systematic literature review by means of Pubmed, Embase, Cochrane and Web of Science and applying the PRISMA guidelines. We classified studies according to selected characteristics (eg, original data, mathematical models, policy papers, overview of the experience with national CT apps) in order to better outline our results. Results Our queries yielded 1201 articles, of which 790 remained after duplicates' removal. After applying a priori selected inclusion criteria, 428 (54.17%) were eliminated after screening by title and abstract. 362 records were included in our study: of them 33.7% were original studies, 54.1% were opinion papers not reporting quantitative data, 14.91% were mathematical models, 6% were systematic reviews on DCT-related topics. Among original studies, 11.47% described national experiences and 25.40% discussed adoption dynamics. Conclusions DCT adoption still faces several cultural, normative and technical barriers, ranging from adoption mandates to privacy issues, to device compatibility. Overall, scant evidence is available on the impact of DCT in controlling infection spread and wide heterogeneity persists within studies in term of design and assessed outcomes Future research is needed based on shared evaluation frameworks. Key messages Digital contact tracing apps are a powerful but underestimated tool to counter epidemiological emergencies. Future epidemiological challenges will require a shared implementation and evaluation protocol for digital contact tracing apps.