Impact of national and regional lockdowns on COVID-19 epidemic waves: Application to the 2020 spring wave in France

Background The efficacy of national lockdowns to control COVID-19 epidemics has been demonstrated. This study aimed at assessing the impact of national and regional lockdowns, in the context of quickly growing pandemic waves, considering the French first wave of the COVID-19 epidemic as a case study. Methods We developed a compartmental epidemic model considering the demographic and age profile of the population of the 13 regions of metropolitan France. We assessed the impact on morbidity, mortality, and hospital resources of simulated national and regional lockdowns starting at different time. Results In a regional lockdown scenario aimed at preventing intensive care units (ICU) saturation in continental France in March 2020, almost all regions would have had to implement a lockdown within 10 days from the actual date of the nationwide implementation. By this date, 97% of ICU capacities would have been used and almost 7000 more lives would have been lost, compared to the March 17 lockdown which limited the mortality burden in hospital to 18 130 deaths. For slowly growing epidemics, with a lower reproduction number, the expected delays between regional lockdowns increases. However, the public health costs associated with these delays tend to grow exponentially with time. Conclusions In a quickly growing pandemic wave, defining the timing of lockdowns at a regional rather than national level delays by a few days the implementation of a nationwide lockdown but leads to substantially higher morbi-mortality and stress on the healthcare system.