title: 2014-2015 Influenza Vaccine Effectiveness in the United States by Vaccine Type.
abstract: BACKGROUND
  Circulating A/H3N2 influenza viruses drifted significantly after strain selection for the 2014-2015 vaccines. Also in 2014-2015, the Advisory Committee on Immunization Practices recommended preferential use of live attenuated influenza vaccine (LAIV) over inactivated influenza vaccine (IIV) among children aged 2-8 years.
  
  
  METHODS
  Vaccine effectiveness (VE) across age groups and vaccine types was examined among outpatients with acute respiratory illness at 5 US sites using a test-negative design, that compared the odds of vaccination among reverse transcription polymerase chain reaction-confirmed influenza positives and negatives.
  
  
  RESULTS
  Of 9311 enrollees with complete data, 7078 (76%) were influenza negative, 1840 (19.8%) were positive for influenza A (A/H3N2, n = 1817), and 395 (4.2%) were positive for influenza B (B/Yamagata, n = 340). The overall adjusted VE was 19% (95% confidence interval [CI], 10% to 27%) and was statistically significant in all age strata except those aged 18-64 years. The adjusted VE of 6% (95%CI, -5% to 17%) against A/H3N2-associated illness was not statistically significant, unlike VE for influenza B/Yamagata, which was 55% (95%CI, 43% to 65%). Among those aged 2-8 years, VE against A/H3N2 was 15% (95%CI, -16% to 38%) for IIV and -3% (CI, -50% to 29%) for LAIV; VE against B/Yamagata was 40% (95%CI, -20% to 70%) for IIV and 74% (95%CI, 25% to 91%) for LAIV.
  
  
  CONCLUSIONS
  The 2014-2015 influenza vaccines offered little protection against the predominant influenza A/H3N2 virus but were effective against influenza B. Preferential use of LAIV among young children was not supported.
authors.affiliation: University of Pittsburgh, Pennsylvania.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Zimmerman
authors.affiliation: University of Pittsburgh, Pennsylvania.
authors.forename: Mary Patricia
authors.initials: MP
authors.lastname: Nowalk
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Jessie
authors.initials: J
authors.lastname: Chung
authors.affiliation: Group Health Research Institute, Seattle, Washington.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Jackson
authors.affiliation: Group Health Research Institute, Seattle, Washington.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Jackson
authors.affiliation: Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor.
authors.forename: Joshua G
authors.initials: JG
authors.lastname: Petrie
authors.affiliation: Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor.
authors.forename: Arnold S
authors.initials: AS
authors.lastname: Monto
authors.affiliation: Marshfield Clinic Research Foundation, Wisconsin.
authors.forename: Huong Q
authors.initials: HQ
authors.lastname: McLean
authors.affiliation: Marshfield Clinic Research Foundation, Wisconsin.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Belongia
authors.affiliation: Baylor Scott and White Health, Texas A&M Health Science Center College of Medicine, Temple.
authors.forename: Manjusha
authors.initials: M
authors.lastname: Gaglani
authors.affiliation: Baylor Scott and White Health, Texas A&M Health Science Center College of Medicine, Temple.
authors.forename: Kempapura
authors.initials: K
authors.lastname: Murthy
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Fry
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Brendan
authors.initials: B
authors.lastname: Flannery
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D000071497:Immunogenicity, Vaccine; D007223:Infant; D053122:Influenza A Virus, H3N2 Subtype; D009980:Influenza A virus; D009981:Influenza B virus; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology; D007251:Influenza, Human / Q000517:prevention & control* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D014481:United States; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000276:immunology; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines; D014613:Vaccines, Attenuated
keywords: influenza vaccine; vaccine effectiveness