Is Lockdown Effective in Limiting SARS-CoV-2 Epidemic Progression?—a Cross-Country Comparative Evaluation Using Epidemiokinetic Tools

International audienceBackground: To date, the risk/benefit balance of lockdown in controlling severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) epidemic is controversial.Objective: We aimed to investigate the effectiveness of lockdown on SARS-CoV-2 epidemic progression in nine different countries (New Zealand, France, Spain, Germany, the Netherlands, Italy, the UK, Sweden, and the USA).Design: We conducted a cross-country comparative evaluation using a susceptible-infected-recovered (SIR)-based model completed with pharmacokinetic approaches.Main measures: The rate of new daily SARS-CoV-2 cases in the nine countries was calculated from the World Health Organization's published data. Using a SIR-based model, we determined the infection (β) and recovery (γ) rate constants; their corresponding half-lives (t1/2β and t1/2γ); the basic reproduction numbers (R0 as β/γ); the rates of susceptible S(t), infected I(t), and recovered R(t) compartments; and the effectiveness of lockdown. Since this approach requires the epidemic termination to build the (I) compartment, we determined S(t) at an early epidemic stage using simple linear regressions.Key results: In New Zealand, France, Spain, Germany, the Netherlands, Italy, and the UK, early-onset stay-at-home orders and restrictions followed by gradual deconfinement allowed rapid reduction in SARS-CoV-2-infected individuals (t1/2β ≤ 14 days) with R0 ≤ 1.5 and rapid recovery (t1/2γ ≤ 18 days). By contrast, in Sweden (no lockdown) and the USA (heterogeneous state-dependent lockdown followed by abrupt deconfinement scenarios), a prolonged plateau of SARS-CoV-2-infected individuals (terminal t1/2β of 23 and 40 days, respectively) with elevated R0 (4.9 and 4.4, respectively) and non-ending recovery (terminal t1/2γ of 112 and 179 days, respectively) was observed.Conclusions: Early-onset lockdown with gradual deconfinement allowed shortening the SARS-CoV-2 epidemic and reducing contaminations. Lockdown should be considered as an effective public health intervention to halt epidemic progression