title: Influenza vaccine effectiveness in the United States during 2012-2013: variable protection by age and virus type.
abstract: BACKGROUND
  During the 2012-2013 influenza season, there was cocirculation of influenza A(H3N2) and 2 influenza B lineage viruses in the United States.
  
  
  METHODS
  Patients with acute cough illness for ≤7 days were prospectively enrolled and had swab samples obtained at outpatient clinics in 5 states. Influenza vaccination dates were confirmed by medical records. The vaccine effectiveness (VE) was estimated as [100% × (1 - adjusted odds ratio)] for vaccination in cases versus test-negative controls.
  
  
  RESULTS
  Influenza was detected in 2307 of 6452 patients (36%); 1292 (56%) had influenza A(H3N2), 582 (25%) had influenza B/Yamagata, and 303 (13%) had influenza B/Victoria. VE was 49% (95% confidence interval [CI], 43%-55%) overall, 39% (95% CI, 29%-47%) against influenza A(H3N2), 66% (95% CI, 58%-73%) against influenza B/Yamagata (vaccine lineage), and 51% (95% CI, 36%-63%) against influenza B/Victoria. VE against influenza A(H3N2) was highest among persons aged 50-64 years (52%; 95% CI, 33%-65%) and persons aged 6 months-8 years (51%; 95% CI, 32%-64%) and lowest among persons aged ≥65 years (11%; 95% CI, -41% to 43%). In younger age groups, there was evidence of residual protection from receipt of the 2011-2012 vaccine 1 year earlier.
  
  
  CONCLUSIONS
  The 2012-2013 vaccines were moderately effective in most age groups. Cross-lineage protection and residual effects from prior vaccination were observed and warrant further investigation.
authors.affiliation: Marshfield Clinic Research Foundation, Wisconsin.
authors.forename: Huong Q
authors.initials: HQ
authors.lastname: McLean
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Thompson
authors.affiliation: Marshfield Clinic Research Foundation, Wisconsin.
authors.forename: Maria E
authors.initials: ME
authors.lastname: Sundaram
authors.affiliation: Marshfield Clinic Research Foundation, Wisconsin.
authors.forename: Burney A
authors.initials: BA
authors.lastname: Kieke
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: Baylor College of Medicine, Houston, Texas.
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Piedra
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: University of Pittsburgh, Pennsylvania.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Raviotta
authors.affiliation: Group Health Cooperative, Seattle, Washington.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Jackson
authors.affiliation: Group Health Cooperative, Seattle, Washington.
authors.forename: Lisa
authors.initials: L
authors.lastname: Jackson
authors.affiliation: University of Michigan, Ann Arbor.
authors.forename: Suzanne E
authors.initials: SE
authors.lastname: Ohmit
authors.affiliation: University of Michigan, Ann Arbor.
authors.forename: Joshua G
authors.initials: JG
authors.lastname: Petrie
authors.affiliation: University of Michigan, Ann Arbor.
authors.forename: Arnold S
authors.initials: AS
authors.lastname: Monto
authors.affiliation: Marshfield Clinic Research Foundation, Wisconsin.
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: Meece
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Swathi N
authors.initials: SN
authors.lastname: Thaker
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Jessie R
authors.initials: JR
authors.lastname: Clippard
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Spencer
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Fry
authors.affiliation: Marshfield Clinic Research Foundation, Wisconsin.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Belongia
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D056738:Cross Protection; D005260:Female; D006801:Humans; D007223:Infant; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D009975:Orthomyxoviridae / Q000276:immunology* / Q000302:isolation & purification*; D016896:Treatment Outcome; D014481:United States; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines
keywords: influenza; medically attended influenza; vaccine effectiveness