Methods: A retrospective claims-based study (GSK study identifier: HO-15-15728) using MarketScan Commercial Database identified influenza cases (ICD-9 487 or 488) occurring between Oct 1 and May 31 during 2010-2014. Eligible children were continuously enrolled for 12 months in a given influenza season (N=68,836). Complications potentially linked to influenza were identified within 21 days after the influenza diagnosis using ICD-9 codes. Influenza cases were matched 1:2 to children without influenza. All-cause and influenza-specific healthcare use and costs were estimated during 21 days of follow-up. Generalized linear models estimated the incremental effect of influenza and complications on healthcare costs.
Results: The seasonal incidence of influenza was 26.8 per 1,000 children (95% CI: 26.6-27.0) with 24.9% experiencing ≥1 influenza-related complication (95% CI: 24.6-25.2). Comparing 68,774 influenza cases to 137,441 matched controls: cases were more likely to have an all-cause hospitalization (1.7% vs. 0.2%) or emergency room (ER) visit (14.0% vs. 2.4%) (all p<0.001). Influenza cases with a complication were more likely to have an influenza-related hospitalization (4.5% vs. 0.7%) or ER visit (19.1% vs. 11.2%) compared to those without a complication (all p<0.001). Adjusting for demographic and clinical characteristics, all-cause costs were higher for influenza cases vs. controls ($902 vs. $496) and influenza-related costs were higher for influenza patients with vs. without complications ($1,160 vs. $386) (all p<0.001).
Conclusion: Children aged 6-35 months with diagnosed influenza experienced higher disease burden than those without influenza; among influenza patients, those who experienced an influenza-related complication had significantly higher costs than those without complications. Better prevention of influenza through improved vaccination coverage could reduce healthcare expenditures in children aged 6-35 months.
R. Shenolikar, GSK: Employee and Shareholder , Salary
AstraZeneca: Employee , Salary
D. Irwin, GSK: Consultant , Research grant