Background: Longstanding recommendations for influenza vaccines among children were augmented by the Advisory Committee on Immunization Practices (ACIP) in 2002 and again in 2008 to encourage vaccination among healthy children aged 6 months-18 years. Little is known about the hospital costs and length of stay among high-risk and otherwise healthy children for the groups affected by the 2002 and 2008 recommendations of the ACIP. The burden of influenza may vary between children with high-risk medical conditions and those who are otherwise healthy. The objective of the current study was to characterize the national burden of influenza hospitalizations and to evaluate how hospital costs and length of stay varied among children diagnosed with influenza.
Methods: A retrospective analysis of influenza hospitalizations was performed in 2006 using the Healthcare Cost and Utilization Project Kids' Inpatient Database, a nationally representative database of hospital discharge records for children from January to December 2003. Children aged <or=18 years with the primary or secondary diagnosis of influenza were classified into three groups based on ACIP recommendations (0-5 months, 6-23 months, 24 months-18 years) and further subdivided by diagnostic codes (asthma, other chronic diseases, without chronic conditions). The outcome measures were aggregate national and mean hospital costs and mean length of stay.
Results: In 2003, aggregate national costs for children with a diagnosis of influenza were $76.5 million, 55% of which was among the group for whom an influenza vaccine was recommended or encouraged in 2003. These costs corresponded to 77,264 inpatient days for 27,363 influenza hospitalizations (2.8 days average length of stay). Mean costs were higher for children with influenza and chronic diseases ($7774) compared to those for children with asthma ($3469) and children without chronic conditions ($2785). Sub-analyses regarding recently expanded national recommendations revealed that 41% of all hospitalizations with a diagnosis of influenza were among otherwise healthy children aged 24 months-18 years.
Conclusions: In 2003, over half of the influenza hospitalizations and costs associated with influenza occurred among children for whom an influenza vaccination was recommended. The frequency of influenza hospitalizations among children aged 24 months-18 years supports recent expansion of the ACIP influenza vaccination recommendations.