title: Effectiveness of seasonal influenza vaccines in the United States during a season with circulation of all three vaccine strains.
abstract: BACKGROUND
  Influenza vaccines may be reformulated annually because of antigenic drift in influenza viruses. However, the relationship between antigenic characteristics of circulating viruses and vaccine effectiveness (VE) is not well understood. We conducted an assessment of the effectiveness of US influenza vaccines during the 2010-2011 season.
  
  
  METHODS
  We performed a case-control study comparing vaccination histories between subjects with acute respiratory illness with positive real-time reverse transcription polymerase chain reaction for influenza and influenza test-negative controls. Subjects with acute respiratory illness of ≤7 days duration were enrolled in hospitals, emergency departments, or outpatient clinics in communities in 4 states. History of immunization with the 2010-2011 vaccine was ascertained from vaccine registries or medical records. Vaccine effectiveness was estimated in logistic regression models adjusted for study community, age, race, insurance status, enrollment site, and presence of a high-risk medical condition.
  
  
  RESULTS
  A total of 1040 influenza-positive cases and 3717 influenza-negative controls were included from the influenza season, including 373 cases of influenza A(H1N1), 334 cases of influenza A(H3N2), and 333 cases of influenza B. Overall adjusted VE was 60% (95% confidence interval [CI], 53%-66%). Age-specific VE estimates ranged from 69% (95% CI, 56%-77%) in children aged 6 months-8 years to 38% (95% CI, -16% to 67%) in adults aged ≥65 years.
  
  
  CONCLUSIONS
  The US 2010-2011 influenza vaccines were moderately effective in preventing medically attended influenza during a season when all 3 vaccine strains were antigenically similar to circulating viruses. Continued monitoring of influenza vaccines in all age groups is important, particularly as new vaccines are introduced.
authors: Department of Medicine, University of Rochester Medical Center, NY, USA. john_treanor@urmc.rochester.edu
authors: John J
authors: JJ
authors: Treanor
authors: H Keipp
authors: HK
authors: Talbot
authors: Suzanne E
authors: SE
authors: Ohmit
authors: Laura A
authors: LA
authors: Coleman
authors: Mark G
authors: MG
authors: Thompson
authors: Po-Yung
authors: PY
authors: Cheng
authors: Joshua G
authors: JG
authors: Petrie
authors: Geraldine
authors: G
authors: Lofthus
authors: Jennifer K
authors: JK
authors: Meece
authors: John V
authors: JV
authors: Williams
authors: Lashondra
authors: L
authors: Berman
authors: Caroline
authors: C
authors: Breese Hall
authors: Arnold S
authors: AS
authors: Monto
authors: Marie R
authors: MR
authors: Griffin
authors: Edward
authors: E
authors: Belongia
authors: David K
authors: DK
authors: Shay
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines