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 <= 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; 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. Our data support the Advisory Committee on Immunization's recommendations to expand the use of influenza vaccine to children > 2 years of age.