The effect of notification window length on the epidemiological impact of COVID-19 contact tracing mobile applications

  1. Trystan Leng
  2. Edward M. Hill
  3. Matt J. Keeling
  4. Michael J. Tildesley
  5. Robin N. Thompson

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Abstract

Background

The reduction in SARS-CoV-2 transmission facilitated by mobile contact tracing applications (apps) depends both on the proportion of relevant contacts notified and on the probability that those contacts quarantine after notification. The proportion of relevant contacts notified depends upon the number of days preceding an infector’s positive test that their contacts are notified, which we refer to as an app’s notification window .

Methods

We use an epidemiological model of SARS-CoV-2 transmission that captures the profile of infection to consider the trade-off between notification window length and active app use. We focus on 5-day and 2-day windows, the notification windows of the NHS COVID-19 app in England and Wales before and after 2nd August 2021, respectively.

Results

Our analyses show that at the same level of active app use, 5-day windows result in larger reductions in transmission than 2-day windows. However, short notification windows can be more effective at reducing transmission if they are associated with higher levels of active app use and adherence to isolation upon notification.

Conclusions

Our results demonstrate the importance of understanding adherence to interventions when setting notification windows for COVID-19 contact tracing apps.

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  1. Version published to 10.1038/s43856-022-00143-2
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    SciScore for 10.1101/2021.11.08.21266079: (What is this?)

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    No key resources detected.

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  3. Version published to 10.1101/2021.11.08.21266079v1 on medRxiv