The epidemiological impact of digital and manual contact tracing on the SARS-CoV-2 epidemic in the Netherlands: Empirical evidence

Wianne Ter Haar; Jizzo Bosdriesz; Roderick P Venekamp; Ewoud Schuit; Susan van den Hof; Wolfgang Ebbers; Mirjam Kretzschmar; Jan Kluijtmans; Carl Moons; Maarten Schim van der Loeff; Amy Matser; Janneke H H M van de Wijgert

doi:10.1371/journal.pdig.0000396

The epidemiological impact of digital and manual contact tracing on the SARS-CoV-2 epidemic in the Netherlands: Empirical evidence

PLOS Digit Health. 2023 Dec 29;2(12):e0000396. doi: 10.1371/journal.pdig.0000396. eCollection 2023 Dec.

Authors

Wianne Ter Haar^{1

2}, Jizzo Bosdriesz^{2

3}, Roderick P Venekamp¹, Ewoud Schuit¹, Susan van den Hof⁴, Wolfgang Ebbers⁵, Mirjam Kretzschmar^{1

4}, Jan Kluijtmans^{1

6}, Carl Moons¹, Maarten Schim van der Loeff^{2

3}, Amy Matser^{2

3}, Janneke H H M van de Wijgert^{1

4}

Affiliations

¹ Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands.
² Public Health Service (GGD) of Amsterdam, Amsterdam, Netherlands.
³ Department of Internal Medicine, Division of Infectious Diseases, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands.
⁴ National Institute for Public Health and the Environment, Bilthoven, Netherlands.
⁵ Department of Public Administration and Sociology, Erasmus University Rotterdam, Rotterdam, Netherlands.
⁶ Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands.

Abstract

The Dutch government introduced the CoronaMelder smartphone application for digital contact tracing (DCT) to complement manual contact tracing (MCT) by Public Health Services (PHS) during the 2020-2022 SARS-CoV-2 epidemic. Modelling studies showed great potential but empirical evidence of DCT and MCT impact is scarce. We determined reasons for testing, and mean exposure-testing intervals by reason for testing, using routine data from PHS Amsterdam (1 December 2020 to 31 May 2021) and data from two SARS-CoV-2 rapid diagnostic test accuracy studies at other PHS sites in the Netherlands (14 December 2020 to 18 June 2021). Throughout the study periods, notification of DCT-identified contacts was via PHS contact-tracers, and self-testing was not yet widely available. The most commonly reported reason for testing was having symptoms. In asymptomatic individuals, it was having been warned by an index case. Only around 2% and 2-5% of all tests took place after DCT or MCT notification, respectively. About 20-36% of those who had received a DCT or MCT notification had symptoms at the time of test request. Test positivity after a DCT notification was significantly lower, and exposure-test intervals after a DCT or MCT notification were longer, than for the above-mentioned other reasons for testing. Our data suggest that the impact of DCT and MCT on the SARS-CoV-2 epidemic in the Netherlands was limited. However, DCT impact might be enlarged if app use coverage is improved, contact-tracers are eliminated from the digital notification process to minimise delays, and DCT is combined with self-testing.

Copyright: © 2023 Ter Haar et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Grants and funding

The authors received no specific funding for the analyses of the routinely collected Public Health Service data. The first and second RDT studies were funded by the Dutch Ministry of Health, Welfare, and Sport (to CM). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.