ABSTRACT. Infections caused by influenza virus lead to an excess rate of hospitalization of children during winter months. Current recommendations for vaccination target only children >6 months who belong to specific risk groups.Objective. To identify possible benefits of universal influenza vaccination, this study aims to determine characteristics of children hospitalized at the Montreal Children's Hospital (MCH) because of an infection attributable to influenza virus as well as risk factors associated with hospitalization.Methods. We retrospectively reviewed records of all children with a laboratory-proven diagnosis of influenza seen at MCH between April 1, 1999, and April 1, 2002. Data were analyzed using the Student t test and logistic regression.Results. We identified 182 patients hospitalized because of influenza and 114 patients who were not. Admission diagnoses were suspected sepsis (31%), lower respiratory tract infections (27%), and asthma or bronchiolitis (15%). Mean age of hospitalized patients was 26.1 month (median: 12 months), which was similar to that of patients not hospitalized, and 34% were <6 months. Seventy percent of those hospitalized did not have any underlying medical disorder and only 18% (33) were vaccine candidates according to current recommendations. Of the latter, less than half had been vaccinated. Factors associated with hospitalization were age <12 months (odds ratio [OR]: 2.3; 95% confidence interval [CI]: 1.1-4.8), male gender (OR: 1.9; 95% CI: 1.0 -3.7), dehydration (OR: 4.3; 95% CI: 1.2-16.0), and decreased oxygen saturation (OR: 32.1; 95% CI: 4.1-249).Conclusions. Considering that the majority of children hospitalized for influenza do not belong to the specific risk groups targeted by current recommendations, and that one third are <6 months of age, the target population for vaccination needs to be reexamined. Extending vaccination to all young children, to additional high-risk groups, and to pregnant women has potential to reduce the impact of influenza on children. Pediatrics 2003;112:e197-e201. URL: http://www.pediatrics.org/cgi/ content/full/112/3/e197; influenza, vaccine, pediatrics, and hospitalization.ABBREVIATIONS. MCH, Montreal Children's Hospital; NPA, nasopharyngeal aspirate; DFA, direct immunofluorescent antigen assay; SD, standard deviation; ICU, intensive care unit; IV, intravenous; LOS, length of stay; OR, odds ratio; CI, confidence interval. I nfluenza is a common disease of childhood with the highest morbidity occurring in preschool children. 1-3 Excess hospitalization rates attributable to influenza infections have been estimated to be 104/10 000 child-years for children Ͻ6 months of age, 50/10 000 for children between 6 and 12 months of age and 19/10 000 for children between 1 and 3 years of age. 4 In another study, excess hospitalizations for healthy children Ͻ2 years of age was 86 to 112/100 000 child-months, 5 a rate similar to that reported for adults over 65 years of age. 6 Higher hospitalization rates are reported for children with underlying high-r...