Less than a month after the identification of the first cases of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in China, the first cases appeared in Europe and thereafter rapidly spread in the world leading to a pandemic [1], [2]. Most countries responded to the first epidemic wave with social distancing measures including strict lockdowns [3]. These constraining measures particularly lockdowns were initially accepted in the context of pandemic with an unknown and lethal virus. Rapidly, concerns rose about their social and economic consequences, mitigating their acceptance and efficacy [3]. The first epidemic wave was followed by subsequent waves, due to the spread of a new dominant virus strain or adaptive health control policies combining social distancing measures and vaccination [4], [5], [6].

Studies on the first pandemic wave identified age, gender and selected chronic comorbidities as main factors of severity and death in patients hospitalized for COVID-19 [7], [8], [9]. These findings informed policies regarding social distancing measures and targeted vaccination in the context of limited availability of vaccine doses against SARS-cov-2. These studies provide clinical characteristics and outcomes for the patients hospitalized for COVID-19 during the first wave as indirect measure of the impact of policies to control the pandemic. In fact, admission to hospital of patients for COVID-19 may indirectly reflect suboptimal preventive measures, while admission to a critical care unit could be viewed as consequences of diagnostic delays or not appropriate care procedures. Comparing patients’ characteristics and outcomes across pandemic waves should indirectly assess the efficiency of the adaptive policies to control the pandemic. Published studies comparing early pandemic waves reported changes in patients’ profile in term of age, sociodemographic characteristics and severity [4], [5], [10]. Further studies are needed to confirm these findings in the long run, especially in the context of constantly evolving epidemic, varying vaccine efficacy and emergence of new virus strains [11].

In this study, we aimed to explore changes in clinical characteristics, admission to critical care unit (CCU) and in-hospital mortality, for patients hospitalised for COVID-19 in France during the successive pandemic waves (from January 2020 to September 2022).