title: The burden of influenza in young children, 2004-2009.
abstract: OBJECTIVE
  To characterize the health care burden of influenza from 2004 through 2009, years when influenza vaccine recommendations were expanded to all children aged ≥6 months.
  
  
  METHODS
  Population-based surveillance for laboratory-confirmed influenza was performed among children aged <5 years presenting with fever and/or acute respiratory illness to inpatient and outpatient settings during 5 influenza seasons in 3 US counties. Enrolled children had nasal/throat swabs tested for influenza by reverse transcriptase-polymerase chain reaction and their medical records reviewed. Rates of influenza hospitalizations per 1000 population and proportions of outpatients (emergency department and clinic) with influenza were computed.
  
  
  RESULTS
  The study population comprised 2970, 2698, and 2920 children from inpatient, emergency department, and clinic settings, respectively. The single-season influenza hospitalization rates were 0.4 to 1.0 per 1000 children aged <5 years and highest for infants <6 months. The proportion of outpatient children with influenza ranged from 10% to 25% annually. Among children hospitalized with influenza, 58% had physician-ordered influenza testing, 35% had discharge diagnoses of influenza, and 2% received antiviral medication. Among outpatients with influenza, 7% were tested for influenza, 7% were diagnosed with influenza, and <1% had antiviral treatment. Throughout the 5 study seasons, <45% of influenza-negative children ≥6 months were fully vaccinated against influenza.
  
  
  CONCLUSIONS
  Despite expanded vaccination recommendations, many children are insufficiently vaccinated, and substantial influenza burden remains. Antiviral use was low. Future studies need to evaluate trends in use of vaccine and antiviral agents and their impact on disease burden and identify strategies to prevent influenza in young infants.
authors.affiliation: Department of Pediatrics, Wake Forest School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, USA. kpoehlin@wakehealth.edu
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Poehling
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Edwards
authors.forename: Marie R
authors.initials: MR
authors.lastname: Griffin
authors.forename: Peter G
authors.initials: PG
authors.lastname: Szilagyi
authors.forename: Mary A
authors.initials: MA
authors.lastname: Staat
authors.forename: Marika K
authors.initials: MK
authors.lastname: Iwane
authors.forename: Beverly M
authors.initials: BM
authors.lastname: Snively
authors.forename: Cynthia K
authors.initials: CK
authors.lastname: Suerken
authors.forename: Caroline B
authors.initials: CB
authors.lastname: Hall
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Weinberg
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Chaves
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Zhu
authors.forename: Monica M
authors.initials: MM
authors.lastname: McNeal
authors.forename: Carolyn B
authors.initials: CB
authors.lastname: Bridges
mesh_terms: D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D017589:Immunization Programs / Q000458:organization & administration / Q000706:statistics & numerical data; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology; D007251:Influenza, Human / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology / Q000517:prevention & control*; D008297:Male; D009518:New York; D009820:Ohio; D010044:Outpatient Clinics, Hospital / Q000706:statistics & numerical data; D011159:Population Surveillance; D011446:Prospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D013714:Tennessee; D014600:Utilization Review / Q000706:statistics & numerical data
chemical_list: D007252:Influenza Vaccines