Introduction - As part of the surveillance of influenza clusters in at-risk communities, the Eastern Regional Office of the French Institute for Public Health Surveillance conducted an investigation in November 2009 at a facility for children and young adults with intellectual disabilities. The objectives were to characterize the outbreak, identify factors contributing to viral transmission, and adapt control measures. Methods - A retrospective cohort study was conducted at the facility, and questionnaires documented sociodemographic and clinical characteristics, transmission factors, and measures taken. Results - The outbreak lasted more than three weeks, with 37 reported cases, the majority of whom were residents (n = 25). The analysis highlighted the increased risk of viral transmission within this type of facility, particularly among residential care residents (RR = 2.2; p = 0.03) and among children under 13 years of age with the most severe disabilities (RR = 4.5; p = 0.002). Despite the early implementation of appropriate barrier measures, the outbreak was only brought under control after the residents and staff were vaccinated and the facility was closed. Discussion - The limited effectiveness of standard control measures calls for a reevaluation of whether such facilities should be considered priority sites for vaccination, not so much because of the children’s vulnerability to the disease, but because of the increased risk of transmission and outbreaks. (R.A.)