The effectiveness of eight nonpharmaceutical interventions against COVID-19 in 41 countries
Author(s)
Type
preprint
Abstract
<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Governments are attempting to control the COVID-19 pandemic with nonpharmaceutical interventions (NPIs). However, it is still largely unknown how effective different NPIs are at reducing transmission. Data-driven studies can estimate the effectiveness of NPIs while minimizing assumptions, but existing analyses lack sufficient data and validation to robustly distinguish the effects of individual NPIs.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We collect chronological data on NPIs in 41 countries between January and May 2020, using independent double entry by researchers to ensure high data quality. We estimate NPI effectiveness with a Bayesian hierarchical model, by linking NPI implementation dates to national case and death counts. To our knowledge, this is the largest and most thoroughly validated data-driven study of NPI effectiveness to date.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>We model each NPI’s effect as a multiplicative (percentage) reduction in the reproduction number <jats:italic>R</jats:italic>. We estimate the mean reduction in R across the countries in our data for eight NPIs: mandating mask-wearing in (some) public spaces (2%; 95% CI: −14%–16%), limiting gatherings to 1000 people or less (2%; −20%–22%), to 100 people or less (21%; 1%–39%), to 10 people or less (36%; 16%–53%), closing some high-risk businesses (31%; 13%–46%), closing most nonessential businesses (40%; 22%–55%), closing schools and universities (39%; 21%–55%), and issuing stay-at-home orders (18%; 4%–31%). These results are supported by extensive empirical validation, including 15 sensitivity analyses.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>Our results suggest that, by implementing effective NPIs, many countries can reduce R below 1 without issuing a stay-at-home order. We find a surprisingly large role for school and university closures in reducing COVID-19 transmission, a contribution to the ongoing debate about the relevance of asymptomatic carriers in disease spread. Banning gatherings and closing high-risk businesses can be highly effective in reducing transmission, but closing most businesses only has limited additional benefit.</jats:p></jats:sec>
Date Issued
2020-05-30
Date Acceptance
2020-07-23
Citation
Cold Spring Harbor Laboratory, 2020
Journal / Book Title
Cold Spring Harbor Laboratory
Copyright Statement
Copyright © 2020 The Author(s). The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC 4.0 International license.
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Publication Status
Published