The impact of lockdown measures on COVID-19: a worldwide comparison

ObjectiveWe aimed to determine which aspects of the COVID-19 national response are independent predictors of COVID-19 mortality and case numbers. DesignComparative observational study between nations using publicly available data. SettingWorldwide Participants Covid-19 patients InterventionsStringency of 11 lockdown policies recorded by the Blavatnik School of Government database and earliness of each policy relative to first recorded national cases Main outcome measuresAssociation with log10 National deaths (LogD) and log10 National cases (LogC) on the 29th April 2020 corrected for predictive demographic variables ResultsEarly introduction was associated with reduced mortality (n=137) and case numbers (n=150) for every policy aside from testing policy, contact tracing and workplace closure. Maximum policy stringency was only found to be associated with reduced mortality (p=0{middle dot}003) or case numbers (p=0{middle dot}010) for international travel restrictions. A multivariate model, generated using demographic parameters (r2=0{middle dot}72 for LogD and r2=0{middle dot}74 for LogC), was used to assess the timing of each policy. Early introduction of first measure (significance p=0{middle dot}048, regression coefficient {beta}=-0{middle dot}004, 95% confidence interval 0 to -0{middle dot}008), early international travel restrictions (p=0{middle dot}042, {beta}=-0{middle dot}005, -0{middle dot}001 to - 0{middle dot}009) and early public information (p=0{middle dot}021, {beta}=-0{middle dot}005, -0{middle dot}001 to -0{middle dot}009) were associated with reduced LogC. Early introduction of first measure (p=0{middle dot}003, {beta}=-0{middle dot}007, -0{middle dot}003 to -0{middle dot}011), early international travel restrictions (p=0{middle dot}003, {beta}=-0{middle dot}008, -0{middle dot}004 to-0{middle dot}012), early public information (p=0{middle dot}003, {beta}=-0{middle dot}007, 0{middle dot}003 to -0{middle dot}011), early generalised workplace closure (p=0{middle dot}031, {beta}=-0{middle dot}012, -0{middle dot}002 to -0{middle dot}022) and early generalised school closure (p=0{middle dot}050, {beta}=-0{middle dot}012, 0 to -0{middle dot}024) were associated with reduced LogC. ConclusionsAt this stage in the pandemic, early institution of public information, international travel restrictions, and workplace closure are associated with reduced COVID-19 mortality and maintaining these policies may help control the pandemic. What is already known on this topicThe COVID-19 pandemic has spread rapidly throughout the world and presented vast healthcare, economic and political challenges. Many nations have recently passed the peak of their infection rate, and are weighing up relaxation of lockdown strategies. Though the effect of individual lockdown policies can be estimated by modelling, little is known about the impact of individual policies on population case numbers or mortality through comparison of differing strategies between nations. A PubMed search was carried out on the 14/5/20 using keywords including "novel coronavirus-infected pneumonia", "2019-nCoV", "Sars-Cov-2", "Covid-19", "lockdown"," policy", "social distancing", "isolation", "quarantine" and "contact tracing" returned 258 studies in total. Following scanning of the above results, we found 19 studies that have examined the effect of lockdown within a region, which have demonstrated a reduction in case numbers after the introduction of a lockdown. There are no previous studies that have compared the effectiveness of government lockdowns between nations to determine the effectiveness of specific policies. What this study addsThis study examines the corollary between government policy and COVID-19 case numbers and mortality, correct as of the 29th of April 2020, for every nation that there is available date within the Blavatnik School of Government database on COVID-19 policy. The study demonstrates that early generalised school closure, early generalised workplace closure, early restriction of international travel and early public information campaigns are independently associated with reduced national COVID-19 mortality. The maximum stringency of individual lockdown policies were not associated with reduced case numbers or mortality. Early reintroduction of these policies may be most effective in a relapse of the pandemic, though, school closure, workplace closure and restriction of international travel carry heavy politico-economic implications. There was no measurable effect of maximum stringency of lockdown policy on outcome at this point in time, indicating that early timing of lockdown introduction is of greater importance than its stringency, provided that the resultant viral reproductive rate is less than 1.