Engagement and adherence trade-offs for SARS-CoV-2 contact tracing.

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Lucas, Tim CD 
Davis, Emma L 
Ayabina, Diepreye 
Borlase, Anna 
Crellen, Thomas 

Contact tracing is an important tool for allowing countries to ease lockdown policies introduced to combat SARS-CoV-2. For contact tracing to be effective, those with symptoms must self-report themselves while their contacts must self-isolate when asked. However, policies such as legal enforcement of self-isolation can create trade-offs by dissuading individuals from self-reporting. We use an existing branching process model to examine which aspects of contact tracing adherence should be prioritized. We consider an inverse relationship between self-isolation adherence and self-reporting engagement, assuming that increasingly strict self-isolation policies will result in fewer individuals self-reporting to the programme. We find that policies which increase the average duration of self-isolation, or that increase the probability that people self-isolate at all, at the expense of reduced self-reporting rate, will not decrease the risk of a large outbreak and may increase the risk, depending on the strength of the trade-off. These results suggest that policies to increase self-isolation adherence should be implemented carefully. Policies that increase self-isolation adherence at the cost of self-reporting rates should be avoided. This article is part of the theme issue 'Modelling that shaped the early COVID-19 pandemic response in the UK'.

COVID-19, SARS-CoV-2, adherence, case isolation, contact tracing, quarantine, Basic Reproduction Number, COVID-19, Communicable Disease Control, Contact Tracing, Disease Outbreaks, Humans, Models, Theoretical, Pandemics, SARS-CoV-2
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Philos Trans R Soc Lond B Biol Sci
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The Royal Society
MRC (via University of Warwick) (MR/V038613/1)