Abstract
Background: Shutdowns are enacted when alternative public health measures are insufficient to control the epidemic and the population is largely susceptible. An age-stratified agent-based model was developed to explore the impact of shutdowns to control SARS-CoV-2 transmission in Canada under the assumption that current efforts to control the epidemic remains insufficient and in the absence of a vaccine. Methods: We estimated the current levels of interventions in Canada to generate a baseline scenario from 7 February to 7 September 2020. Four aspects of shutdowns were explored in scenarios that ran from 8 September 2020 to 7 January 2022, these included the impact of how quickly shutdowns are implemented, the duration of shutdowns, the minimum break (delays) between shutdowns and the types of sectors to shutdown. Comparisons among scenarios were made using cases, hospitalizations, deaths and shutdown days during the 700-day model runs. Results: We found a negative relationship between reducing SARS-CoV-2 transmission and the number of shutdown days. However, we also found that for shutdowns to be optimally effective, they need to be implemented fast with minimal delay, initiated when community transmission is low, sustained for an adequate period and be stringent and target multiple sectors, particularly those driving transmission. By applying shutdowns in this manner, the total number of shutdown days could be reduced compared to delaying the shutdowns until further into the epidemic when transmission is higher and/or implementing short insufficient shutdowns that would require frequent re-implementation. This paper contrasts a range of shutdown strategies and trade-offs between health outcomes and economic metrics that need to be considered within the local context. Interpretation: Given the immense socioeconomic impact of shutdowns, they should be avoided where possible and used only when other public health measures are insufficient to control the epidemic. If used, the time it buys to delay the epidemic should be used to enhance other equally effective, but less disruptive, public health measures.
Highlights
As coronavirus disease (COVID-19) continues to spread globally with the resurgence of cases in many countries, multiple public health interventions that were employed during the initial months of the epidemic are being re-implemented [1]
Scenario 1: speed of shutdowns total attack rate (%) clinical attack rate (%) asymptomatic attack rate (%) case fatality rate (%) infection fatality rate (%) number of shutdown days total cases per 100 000 total clinical cases per 100 000 total asymptomatic cases per 100 000 total hospitalized cases per 100 000 total acute hospitalized cases per 100 000 total cases admitted into the ICU per 100 000 total deaths per 100 000 proportion of infections acquired at school (%) proportion of infections acquired at work (%) proportion of infections acquired in mixed-age venues (%) proportion of infections acquired in the household (%)
Scenario 2: duration of shutdowns total attack rate (%) clinical attack rate (%) asymptomatic attack rate (%) case fatality rate (%) infection fatality rate (%) number of shutdown days total cases per 100 000 total clinical cases per 100 000 total asymptomatic cases per 100 000 total hospitalized cases per 100 000 total acute hospitalized cases per 100 000 total cases admitted into the ICU per 100 000 total deaths per 100 000 proportion of infections acquired at school (%) proportion of infections acquired at work (%) proportion of infections acquired in mixed-age venues (%) proportion of infections acquired in the household (%)
Summary
As coronavirus disease (COVID-19) continues to spread globally with the resurgence of cases in many countries, multiple public health interventions that were employed during the initial months of the epidemic are being re-implemented [1]. Studies have projected that when restrictive closures are lifted in Canada, if alternative public health measures such as detection and isolation of cases, and tracing and quarantining of close contacts of cases are insufficient, subsequent waves of infections will occur [5,6,7]. These modelled projections have unfolded in reality in recent months across Canada as many provinces struggle to regain control of the epidemic [8].
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