The autumnal lockdown was not the main initiator of the decrease in SARS-CoV-2 circulation in France

BACKGROUND: In response to the SARS-CoV-2 pandemic, governments have taken drastically restrictive public health measures with significant collateral effects. It is important to understand the impact of these measures on SARS-CoV-2 circulation. However, pandemic indicators lag behind the actual level of viral circulation and these delays are an obstacle to assessing the effectiveness of policy decisions. Here, we propose one way to solve this problem by synchronizing the indicators with viral circulation in a country (France) based on a landmark event. METHODS: Based on a first lockdown, we measured the time lag between the peak of governmental and non-governmental surveillance indicators and the highest level of virus circulation. This allowed alignment of all surveillance indicators with viral circulation during the second period of the epidemic, overlaid with the type of public health measures implemented. RESULTS: We show that the second peak in viral circulation in France happened ~21 October 2020, during the public health state of emergency but before the lockdown (31 October). Indicators also suggest that viral circulation decreased earlier in locations where curfews were implemented. Indicators did, however, begin to rise once the autumnal lockdown was lifted and the state of emergency resumed. CONCLUSIONS: Overall, these results suggest that in France, the 2020 autumnal lockdown was not the main initiator of the decrease in SARS-CoV-2 circulation and curfews were important in achieving control of the transmission. Less-restrictive measures may need to be balanced with more-stringent measures to achieve desirable public health outcomes over time.