title: Influenza-related hospitalization and ED visits in children less than 5 years: 2000-2011.
abstract: OBJECTIVE
  In the United States, recommendations for annual influenza vaccination gradually expanded from 2004 to 2008, to include all children aged ≥6 months. The effects of these policies on vaccine uptake and influenza-associated health care encounters are unclear. The objectives of the study were to examine the annual incidence of influenza-related health care encounters and vaccine uptake among children age 6 to 59 months from 2000-2001 through 2010-2011 in Davidson County, TN.
  
  
  METHODS
  We estimated the proportion of laboratory-confirmed influenza-related hospitalizations and emergency department (ED) visits by enrolling and testing children with acute respiratory illness or fever. We estimated influenza-related health care encounters by multiplying these proportions by the number of acute respiratory illness/fever hospitalizations and ED visits for county residents. We assessed temporal trends in vaccination coverage, and influenza-associated hospitalizations and ED visit rates.
  
  
  RESULTS
  The proportion of fully vaccinated children increased from 6% in 2000-2001 to 38% in 2010-2011 (P < .05). Influenza-related hospitalizations ranged from 1.9 to 16.0 per 10 000 children (median 4.5) per year. Influenza-related ED visits ranged from 89 to 620 per 10 000 children (median 143) per year. Significant decreases in hospitalizations (P < .05) and increases in ED visits (P < .05) over time were not clearly related to vaccination trends. Influenza-related encounters were greater when influenza A(H3N2) circulated than during other years with median rates of 8.2 vs 3.2 hospitalizations and 307 vs 143 ED visits per 10 000 children, respectively.
  
  
  CONCLUSIONS
  Influenza vaccination increased over time; however, the proportion of fully vaccinated children remained <50%. Influenza was associated with a substantial illness burden particularly when influenza A(H3N2) predominated.
authors.affiliation: Departments of Health Policy.
authors.forename: Astride
authors.initials: A
authors.lastname: Jules
authors.affiliation: Departments of Health Policy.
authors.forename: Carlos G
authors.initials: CG
authors.lastname: Grijalva
authors.affiliation: Biostatistics.
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Medicine.
authors.forename: H Keipp
authors.initials: HK
authors.lastname: Talbot
authors.affiliation: Pediatrics, and Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee;
authors.forename: John V
authors.initials: JV
authors.lastname: Williams
authors.affiliation: Departments of Pediatrics and Epidemiology and Prevention, Wake Forest School of Medicine, Winston-Salem, North Carolina; and.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Poehling
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Chaves
authors.affiliation: Pediatrics, and.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Edwards
authors.affiliation: Departments of Health Policy.
authors.forename: William
authors.initials: W
authors.lastname: Schaffner
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: David K
authors.initials: DK
authors.lastname: Shay
authors.affiliation: Departments of Health Policy, Medicine, marie.griffin@vanderbilt.edu.
authors.forename: Marie R
authors.initials: MR
authors.lastname: Griffin
mesh_terms: D002675:Child, Preschool; D004630:Emergencies / Q000453:epidemiology; D004636:Emergency Service, Hospital; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007223:Infant; D053122:Influenza A Virus, H3N2 Subtype; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control; D008297:Male; D012621:Seasons; D013997:Time Factors; D014611:Vaccination / Q000706:statistics & numerical data
chemical_list: D007252:Influenza Vaccines
keywords: hospitalization; influenza; rate; ratio; vaccination coverage