Epidemiology, complications, and cost of hospitalization in children with laboratory-confirmed influenza infection.

BACKGROUND: Influenza causes significant morbidity among children. Previous studies used indirect case ascertainment methods with little cost data. We sought to measure the burden of laboratory-confirmed influenza from hospitalized children. METHODS: We conducted a retrospective cohort study during 3 viral seasons at Primary Children's Medical Center (Salt Lake City, UT). Children < or = 18 years of age who were hospitalized with laboratory-confirmed influenza infection were included. Outcomes included hospitalization rates, complications including intensive care unit stays, mechanical ventilation, length of stay, and total hospital costs. RESULTS: A total of 325 children had hospitalizations attributable to influenza over 3 viral seasons: 28% < 6 months of age, 33% between 6 and 23 months of age; and 39% > 2 years of age; 37% had high-risk medical conditions. Population-based rates of hospitalization for Salt Lake County residents ranged from 6.3 to 252.7 per 100,000 children. The highest rates were in children younger than 6 months, and rates decreased with increasing age. Forty-nine (15%) children had an ICU stay; 27 required mechanical ventilation, and half of these patients were > 2 years of age. Total hospital cost for the cohort was 2 million dollars; 55% was accounted for by children > 2 years of age. Length of stay and total hospital costs were significantly higher in all children > 2 years of age compared with children < 6 months of age and were comparable to all children 6 to 23 months of age. CONCLUSIONS: Proven influenza infection in children results in substantial hospital resource utilization and morbidity. Nationwide, the median hospital costs may total 55 million dollars. Our data support the Advisory Committee on Immunization's recommendations to expand the use of influenza vaccine to children > 2 years of age.