The epidemiological impact of digital and manual contact tracing on the SARS-CoV-2 epidemic in the Netherlands: empirical evidence.
Background. 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. Methods. 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. Results. 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. Conclusions. 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.
### Competing Interest Statement
JHHMvdW, JK, and CM were members of the Dutch Ministry of Health, Welfare, and Sport advisory committee on digital support of SARS-CoV-2 control. WE was a member of the Dutch Ministry of Health, Welfare, and Sport task force on digital support of SARS-CoV-2 control, and was commissioned by the Dutch Ministry of Health, Welfare and Sport to evaluate CoronaMelder.
### Funding Statement
The first and second RDT studies were funded by the Dutch Ministry of Health, Welfare, and Sport. The funder had no role in study design; data collection and analysis, decision to publish, or preparation of the manuscript.
### Author Declarations
I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.
Yes
The details of the IRB/oversight body that provided approval or exemption for the research described are given below:
The Medical Ethics Committee of the University Medical Center Utrecht, the Netherlands, determined that ethical approval was not needed because the studies fell outside the scope of the Dutch Medical Research Involving Human Subjects Act (protocol No 20/750).
I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.
Yes
I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).
Yes
I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.
Yes
PHS Amsterdam data are not publicly available for privacy reasons. Individual participant data of the two RDT studies will be made available, after deidentification, to researchers who provide a methodologically sound proposal. Proposals should be directed to Professor Carl Moons ([email protected]). Data requestors will need to sign a data access agreement.
Kloosterboer
Arie van Deursen
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André Koot RCX
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