COVID-19 clusters in a teaching hospital during the second wave of the SARS-CoV-2 pandemic in France: A descriptive study and lessons learned for waves to come.

A total of 92 coronavirus disease 2019 clusters involving 1,156 individuals (729 patients and 427 healthcare workers) occurred in Lyon University Hospital between September 1, 2020 and March 31, 2021, mostly on medical and geriatric wards. The number of clusters was closely correlated to the trend in coronavirus disease 2019 community incidence over time; in-hospital clusters did not persist when community incidence decreased. Recommended preventive measures were not fully applicable due to specific ward-associated determinants and patient characteristics.