Sustainable Border Control Policy in the COVID-19 Pandemic: A Math Modeling Study

TL;DR

This study develops a mathematical model to evaluate sustainable border control strategies during COVID-19 reopening phases, emphasizing the importance of combined domestic measures and contact tracing to prevent outbreaks without reverting to strict restrictions.

Contribution

It introduces the SUIHR model, an extension of SIR models, to analyze virus spread considering asymptomatic transmission, imported cases, and contact tracing, providing insights into sustainable border policies.

Findings

Border control alone is insufficient when R0 exceeds 2.5.

Strict pre-departure screening delays outbreaks by approximately 6 months.

Effective domestic measures can contain cases without border restrictions.

Abstract

Imported COVID-19 cases, if unchecked, can jeopardize the effort of domestic containment. We aim to find out what sustainable border control options for different entities (e.g., countries, states) exist during the reopening phases, given their own choice of domestic control measures and new technologies such as contact tracing. We propose a SUIHR model, which represents an extension to the discrete time SIR models. The model focuses on studying the spreading of virus predominantly by asymptomatic and pre-symptomatic patients. Imported risk and (1-tier) contact tracing are both built into the model. Under plausible parameter assumptions, we seek sustainable border control policies, in combination with sufficient internal measures, which allow entities to confine the virus without the need to revert back to more restrictive life styles or to rely on herd immunity. When the base reproduction number of COVID-19 exceeds 2.5, even 100% effective contact tracing alone is not enough to contain the spreading. For an entity that has completely eliminated the virus domestically, and resumes "normal", very strict pre-departure screening and test and isolation upon arrival combined with effective contact tracing can only delay another outbreak by 6 months. However, if the total net imported cases are non-increasing, and the entity employs a confining domestic control policy, then the total new cases can be contained even without border control.