Analysing different exposures identifies that wearing masks and establishing COVID-19 areas reduce secondary-attack risk in aged-care facilities Reyne, B. /Selinger, Christian Sofonea, M. T. Miot, S. Pisoni, A. Tuaillon, E. Bousquet, J. Blain, H. Alizon, S. COVID-19 aged-care facilities mask wearing generalized linear mixed models secondary-attack risk Background: The COVID-19 epidemic has spread rapidly within aged-care facilities (ACFs), where the infection-fatality ratio is high. It is therefore urgent to evaluate the efficiency of infection prevention and control (IPC) measures in reducing SARS-CoV-2 transmission. Methods: We analysed the COVID-19 outbreaks that took place between March and May 2020 in 12 ACFs using reverse transcription-polymerase chain reaction (RT-PCR) and serological tests for SARS-CoV-2 infection. Using maximum-likelihood approaches and generalized linear mixed models, we analysed the proportion of infected residents in ACFs and identified covariates associated with the proportion of infected residents. Results: The secondary-attack risk was estimated at 4.1%, suggesting a high efficiency of the IPC measures implemented in the region. Mask wearing and the establishment of COVID-19 zones for infected residents were the two main covariates associated with lower secondary-attack risks. Conclusions: Wearing masks and isolating potentially infected residents appear to be associated with a more limited spread of SARS-CoV-2 in ACFs. 2021 text https://www.documentation.ird.fr/hor/fdi:010084235 fdi:010084235 Reyne B., Selinger Christian, Sofonea M. T., Miot S., Pisoni A., Tuaillon E., Bousquet J., Blain H., Alizon S.. Analysing different exposures identifies that wearing masks and establishing COVID-19 areas reduce secondary-attack risk in aged-care facilities. 2021, 50 (6), 1788-1794 EN FRANCE