Optimal targeting of interventions uses estimated risk of infectiousness to control a pandemic with minimal collateral damage

In this paper, we present a simple model that shows how to optimally target interventions based on the estimated risk of infectiousness of individuals. Our model can help policymakers decide when to use different types of interventions during a pandemic, depending on their precision, which is the fraction of positive predictions that are true positives. We show that targeted interventions, even with very low precision, can impose a much smaller overall burden on the population than non-targeted alternatives, such as lockdowns or mass testing. To illustrate this, we use data from the NHS contact tracing system in the UK to construct a risk function based on second degree contact tracing, which is similar to the strategy used by Vietnam in 2020. We find that with moderate precision (greater than 1/1000) and sufficient sensitivity (greater than 1 − 1 /R ), countries can cope with a large number of imported cases without resorting to social distancing measures, while keeping the per-person probabilities of both infection and quarantine very low. We also show that targeted strategies are often orders of magnitude better than default strategies, making them robustly beneficial even under significant uncertainty about most parameters. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study did not receive any funding ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the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 All code and data used for this manuscript are available at