Does city lockdown prevent the spread of COVID-19? New evidence from the synthetic control method
Tóm tắt
At 10 a.m. on January 23, 2020 Wuhan, China imposed a 76-day travel lockdown on its 11 million residents in order to stop the spread of COVID-19. This lockdown represented the largest quarantine in the history of public health and provides us with an opportunity to critically examine the relationship between a city lockdown on human mobility and controlling the spread of a viral epidemic, in this case COVID-19. This study aims to assess the causal impact of the Wuhan lockdown on population movement and the increase of newly confirmed COVID-19 cases. Based on the daily panel data from 279 Chinese cities, our research is the first to apply the synthetic control approach to empirically analyze the causal relationship between the Wuhan lockdown of its population mobility and the progression of newly confirmed COVID-19 cases. By using a weighted average of available control cities to reproduce the counterfactual outcome trajectory that the treated city would have experienced in the absence of the lockdown, the synthetic control approach overcomes the sample selection bias and policy endogeneity problems that can arise from previous empirical methods in selecting control units. In our example, the lockdown of Wuhan reduced mobility inflow by approximately 60 % and outflow by about 50 %. A significant reduction of new cases was observed within four days of the lockdown. The increase in new cases declined by around 50% during this period. However, the suppression effect became less discernible after this initial period of time. A 2.25-fold surge was found for the increase in new cases on the fifth day following the lockdown, after which it died down rapidly. Our study provided urgently needed and reliable causal evidence that city lockdown can be an effective short-term tool in containing and delaying the spread of a viral epidemic. Further, the city lockdown strategy can buy time during which countries can mobilize an effective response in order to better prepare. Therefore, in spite of initial widespread skepticism, lockdowns are likely to be added to the response toolkit used for any future pandemic outbreak.
Tài liệu tham khảo
Chen S, Yang J, Yang W, Wang C, Bärnighausen T. COVID-19 control in China during mass population movements at New Year. The Lancet. 2020;395(10226):764–6.
Yang, X. Timing and Support Safeguards for Reopening an Economy During COVID-19. World Journal of Public Health. 2021a;6(2):31–9.
Yang, X. COVID-19 Cannot Sustainably Improve Air Quality: Evidence from Reopening an Economy. Journal of Health and Environmental Research. 2021b;7(2):94–104.
Li R, Pei S, Chen B, Song Y, Zhang T, Yang W, et al. Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV-2). Science. 2020;368(6490):489–93.
Center for Disease Control and Prevention. About Variants of the Virus that Causes COVID-19. 2 Apr 2021. Available from: https://www.cdc.gov/coronavirus/2019-ncov/transmission/variant.html. Accessed 10 May 2021.
Kirby T. New variant of SARS-CoV-2 in UK causes surge of COVID-19. The Lancet Respiratory Medicine. 2021;9(2):e20–e21.
BBC. India Covid: Government says new variant linked to surge. 6 May 2021. Available from: https://www.bbc.com/news/world-asia-india-57004764. Accessed 10 May 2021.
Chan JF, Yuan S, Kok KH, To KK, Chu H, Yang J, et al. A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster. The Lancet. 2020;395(10223):514–23.
Bajardi P, Poletto C, Ramasco JJ, Tizzoni M, Colizza V, Vespignani A. Human mobility networks, travel restrictions, and the global spread of 2009 H1N1 pandemic. PloS One. 2011;6(1):e16591.
Wang Q, Taylor JE. Patterns and limitations of urban human mobility resilience under the influence of multiple types of natural disaster. PLoS One. 2016;11(1):e0147299.
Charu V, Zeger S, Gog J, Bjørnstad ON, Kissler S, Simonsen L, et al. Human mobility and the spatial transmission of influenza in the United States. PLoS Computational Biology. 2017;13(2):e1005382.
Fang H, Wang L, Yang Y. Human mobility restrictions and the spread of the novel coronavirus (2019-ncov) in china. Journal of Public Economics. 2020;191:104272.
Ferguson NM, Cummings DA, Fraser C, Cajka JC, Cooley PC, Burke DS. Strategies for mitigating an influenza pandemic. Nature. 2006;442(7101):448–52.
Hollingsworth TD, Ferguson NM, Anderson RM. Will travel restrictions control the international spread of pandemic influenza? Nature Medicine. 2006;12(5):497–9.
Qiu Y, Chen X, Shi W. Impacts of social and economic factors on the transmission of coronavirus disease 2019 (COVID-19) in China. Journal of Population Economics. 2020;33:1127–72.
Chinazzi M, Davis JT, Ajelli M, Gioannini C, Litvinova M, Merler S, et al. The effect of travel restrictions on the spread of the 2019 novel coronavirus (COVID-19) outbreak. Science. 2020;368(6489):395–400.
Lai S, Ruktanonchai NW, Zhou L, Prosper O, Luo W, Floyd JR, et al. Effect of non-pharmaceutical interventions to contain COVID-19 in China. Nature. 2020;585(7825):410–3.
Abadie A, Gardeazabal J. The economic costs of conflict: A case study of the Basque Country. American Economic Review. 2003;93(1):113–32.
Abadie A, Diamond A, Hainmueller J. Synthetic control methods for comparative case studies: Estimating the effect of California’s tobacco control program. Journal of the American Statistical Association. 2010;105(490):493–505.
Abadie A. Using synthetic controls: Feasibility, data requirements, and methodological aspects. Journal of Economic Literature. 2021;59(2):391–425.
Cole MA, Elliott RJ, Liu B. The impact of the Wuhan Covid-19 lockdown on air pollution and health: a machine learning and augmented synthetic control approach. Environmental and Resource Economics. 2020;76(4):553–80.
Athey S, Imbens GW. The state of applied econometrics: Causality and policy evaluation. Journal of Economic Perspectives. 2017;31(2):3–32.
Bertrand M, Duflo E, Mullainathan S. How much should we trust differences-in-differences estimates? The Quarterly Journal of Economics. 2004;119(1):249–75.
Backer JA, Klinkenberg D, Wallinga J. Incubation period of 2019 novel coronavirus (2019-nCoV) infections among travellers from Wuhan, China, 20–28 January 2020. Eurosurveillance. 2020;25(5):2000062.
Guan WJ, Ni ZY, Hu Y, Liang WH, Ou CQ, He JX, et al. Clinical characteristics of 2019 novel coronavirus infection in China. MedRxiv. 2020.
Kraemer MU, Yang CH, Gutierrez B, Wu CH, Klein B, Pigott DM, et al. The effect of human mobility and control measures on the COVID-19 epidemic in China. Science. 2020;368(6490):493–7.
Lauer SA, Grantz KH, Bi Q, Jones FK, Zheng Q, Meredith HR, et al. The incubation period of coronavirus disease 2019 (COVID-19) from publicly reported confirmed cases: estimation and application. Annals of Internal Medicine. 2020;172(9):577–82.
Reuters. Wuhan lockdown ‘unprecedented’ shows commitment to contain virus: WHO representative in China. 23 Jan 2020. Available from:https://www.reuters.com/article/us-china-health-who-idUSKBN1ZM1G9. Accessed 9 May 2021.
Amnesty International. Explainer: Seven ways the coronavirus affects human rights. 5 Feb 2020. Available from: https://www.amnesty.org/en/latest/news/2020/02/explainer-seven-ways-the-coronavirus-affects-human-rights/. Accessed 9 May 2021.
Oddone E. Italy struggles with virus ‘that doesn’t respect borders’. Al Jazeera. 16 Feb 2020. Available from: https://www.aljazeera.com/features/2020/2/26/italy-struggles-with-virus-that-doesnt-respect-borders. Accessed 9 May 2021.
Shi JT. South China Morning Post. Fears mount as coronavirus outbreak worsens in sanctions-hit Iran. South China Morning Post. 25 Feb 2020. Available from:https://www.scmp.com/news/china/diplomacy/article/3052152/fears-mount-coronavirus-outbreak-worsens-sanctions-hit-iran. Accessed 9 May 2021.
Mehrotra K. Dr Anthony S Fauci on India’s Covid Crisis: ‘Shut down the country for a few weeks…hang in there, take care of each other, we’ll get to a normal’. The Indian Express. 1 May 2021. Available from: https://indianexpress.com/article/express-exclusive/indias-covid-crisis-anthony-s-fauci-coronavirus-death-7297380/. Accessed 9 May 2021.