Maintenance Notice

Due to necessary scheduled maintenance, the JMIR Publications website will be unavailable from Wednesday, July 01, 2020 at 8:00 PM to 10:00 PM EST. We apologize in advance for any inconvenience this may cause you.

Who will be affected?

Accepted for/Published in: JMIR Public Health and Surveillance

Date Submitted: Dec 12, 2021
Date Accepted: Apr 26, 2022
Date Submitted to PubMed: Apr 27, 2022

The final, peer-reviewed published version of this preprint can be found here:

Individual-Level Evaluation of the Exposure Notification Cascade in the SwissCovid Digital Proximity Tracing App: Observational Study

Ballouz T, Menges D, Aschmann HE, Jung R, Domenghino A, Fehr JS, Puhan MA, von Wyl V

Individual-Level Evaluation of the Exposure Notification Cascade in the SwissCovid Digital Proximity Tracing App: Observational Study

JMIR Public Health Surveill 2022;8(5):e35653

DOI: 10.2196/35653

PMID: 35476726

PMCID: 9122110

Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.

Individual-level Evaluation of the Exposure Notification Cascade in the SwissCovid Digital Proximity Tracing App: An Observational Study

  • Tala Ballouz; 
  • Dominik Menges; 
  • Hélène E Aschmann; 
  • Ruedi Jung; 
  • Anja Domenghino; 
  • Jan S Fehr; 
  • Milo Alan Puhan; 
  • Viktor von Wyl

ABSTRACT

Background:

Digital proximity tracing (DPT) aims to complement manual contact tracing (MCT) in identifying exposed contacts and preventing further transmission of SARS-CoV-2 in the population. While several DPT apps, including SwissCovid, have shown to have promising effects on mitigating the pandemic, several challenges have impeded them from fully achieving the desired results. A key question now relates to how the effectiveness of DPT can be improved which requires better understanding of factors influencing its processes.

Objective:

In this study, we aimed to provide a detailed examination of the exposure notification (EN) cascade and to evaluate potential contextual influences for successful receipt of EN and subsequent actions taken by cases and contacts in different exposure settings.

Methods:

We used data from 285 pairs of SARS-CoV-2-infected cases and their contacts within an observational cohort study of cases and contacts identified by MCT and enrolled between 06 August and 17 January 2021 in the Canton of Zurich, Switzerland. We surveyed participants with electronic questionnaires. Data were summarized descriptively and stratified by exposure setting.

Results:

We found that only 60% of contacts using the app whose corresponding case reported to have triggered the EN also received one. Among those, 23% received the EN before being contacted by MCT. Compared to those receiving an EN after MCT, we observed that a higher proportion of contacts receiving an EN before MCT were exposed in non-household settings (67% versus 56%) and their corresponding cases had more frequently reported mild to moderate symptoms (78% versus 69%). Among the 18 contacts receiving an EN before MCT, 14 (78%) took preventive measures: 12 (67%) were tested for SARS-CoV-2 and 7 (39%) called the SwissCovid Infoline. In non-household settings, the proportion of contacts taking preventive actions after receiving an EN was higher compared to same-household settings (82% versus 67%). One in eleven ENs received before MCT led to the identification of a SARS-CoV-2-infected case by prompting the contact to get tested. This corresponds to one in 85 exposures of a contact to a case in a non-household setting, in which both were app users and the case triggered the EN.

Conclusions:

Our descriptive evaluation of the DPT notification cascade provides further evidence that DPT is an important complementary tool in pandemic mitigation, especially in non-household exposure settings. However, the effect of DPT apps can only be exerted if code generation processes are efficient and exposed contacts are willing to undertake preventive actions. This highlights the need to focus efforts on keeping barriers to efficient code generation as low as possible and promoting not only app adoption but also compliance with the recommended measures upon EN. Clinical Trial: ISRCTN14990068


 Citation

Please cite as:

Ballouz T, Menges D, Aschmann HE, Jung R, Domenghino A, Fehr JS, Puhan MA, von Wyl V

Individual-Level Evaluation of the Exposure Notification Cascade in the SwissCovid Digital Proximity Tracing App: Observational Study

JMIR Public Health Surveill 2022;8(5):e35653

DOI: 10.2196/35653

PMID: 35476726

PMCID: 9122110

Download PDF


Request queued. Please wait while the file is being generated. It may take some time.

© The authors. All rights reserved. This is a privileged document currently under peer-review/community review (or an accepted/rejected manuscript). Authors have provided JMIR Publications with an exclusive license to publish this preprint on it's website for review and ahead-of-print citation purposes only. While the final peer-reviewed paper may be licensed under a cc-by license on publication, at this stage authors and publisher expressively prohibit redistribution of this draft paper other than for review purposes.