Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Canada. Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada. Department of Medicine, University of Ottawa, Ottawa, Canada. Division of Pediatric Critical Care Medicine, Department of Pediatrics, Université de Montréal, Montreal, Canada. Unité de Recherche Clinique Appliquée, Université de Montréal, Centre de Recherche, CHU Sainte-Justine, Montreal, Canada. Division of Pediatric Infectious Diseases, Department of Pediatrics, McGill University, Montreal, Canada. Division of Pediatric Critical Care Medicine, Department of Pediatrics, McGill University, Montreal, Canada.