Lockdown impact on COVID-19 epidemics in regions across metropolitan France

Lockdowns have been used by most European countries in response to the COVID-19 pandemic. In France, a national lockdown was implemented on March 17, 2020. Some have questioned the need for a nationwide implementation given that most hospital admissions were concentrated in two of 13 regions; others have even questioned the impact of the lockdown on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spread, arguing that the natural epidemic peak was about to be reached. Here we discuss the impact of lockdown on COVID-19 epidemics in regions across metropolitan France.

On March 17, 2020, daily hospital admissions were indeed highest in Grand-Est (5·3 per 100 000 inhab­itants) and Île-de-France (3·6 per 100 000 inhabitants) regions. Yet a surge in COVID-19 hospital admissions was occurring at that time across all regions of metropolitan France, as depicted in the appendix. The COVID-19 epidemic spread from the eastern to the western parts of France, crossing the daily hospitalisation threshold of 1 per 100 000 inhabitants between March 10 (Grand-Est) and March 23, 2020 (Bretagne and Nouvelle-Aquitaine). Île-de-France (Paris region) experienced the highest rate of hos­pital admissions per day (10·0 per 100 000 inhabitants), and Bretagne the lowest (1·3 per 100 000 inhabitants). Regardless of the time the epidemic started in the region, and its scale, 12 of 13 regions experienced a peak in daily hospital admissions on average 11 days (range 8–14 days) after the lockdown was implemented. This figure corresponds to the mean duration between infection and hospital admission for the patients experiencing severe forms of disease.¹ Since the different regions were at different stages of the pandemic at the time the lockdown was imple­mented, the synchrony in regional peaks strongly suggests that the lockdown, rather than the natural course of the epidemic, explains the peak in hospital admissions. Moreover, most regions were experiencing exponential growth in hospital admissions (appendix), such that saturation of local intensive care units might have occurred in those regions in the absence of any lockdown.

Lockdown therefore appears to have been successful not only in alleviating the burden on the intensive care units of the two most severely affected regions of France, but also in preventing uncontrolled epidemics in other regions. These simple obser­vations support results from other studies which have estimated the impact of lockdown on SARS-CoV-2 spread to be strong.2, 3, 4, 5 Enforcement of public health and social measures in combination with important testing, tracing, and isolating capacities will be critical in case of an epidemic rebound to avoid re-introducing a lockdown—a situation for which the economic cost and broader impact on society are considerable.