title: Effectiveness of seasonal vaccine in preventing confirmed influenza-associated hospitalizations in community dwelling older adults.
abstract: BACKGROUND
  Current evidence supporting the effectiveness of influenza vaccine in preventing hospitalizations in older adults is insufficient.
  
  
  METHODS
  During 3 influenza seasons, 2006-2009, community-dwelling adults aged ≥50 y hospitalized with respiratory symptoms were prospectively enrolled in this study. We tested nose and throat samples for influenza virus by reverse transcriptase-polymerase chain reaction. We estimated vaccine effectiveness by comparing vaccination status between influenza-positive cases and influenza-negative controls using logistic regression models with propensity score adjustment.
  
  
  RESULTS
  Overall, 450 (59%) of 763 eligible patients were enrolled; 417 (93%) of enrolled patients had adequate respiratory samples, had known influenza vaccination status, and were community-dwelling. The proportions of influenza-positive patients were 8%, 20%, and 6% in the 3 successive seasons. Of 39 influenza-positive participants, 14 (36%) were vaccinated compared with 250 (66%) of 378 influenza-negative controls. Propensity score-adjusted vaccine effectiveness for the 3 seasons combined was 61.2% (95% confidence interval, 17.5%-81.8%).
  
  
  CONCLUSIONS
  Overall, in this moderately well-vaccinated population of older adults, laboratory-confirmed influenza virus accounted for 9.3% (95% confidence interval, 6.6%-12.1%) of all respiratory hospitalizations during 3 influenza seasons, and influenza vaccination prevented 61.2% of such hospitalizations.
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA. keipp.talbot@vanderbilt.edu
authors.forename: H Keipp
authors.initials: HK
authors.lastname: Talbot
authors.forename: Marie R
authors.initials: MR
authors.lastname: Griffin
authors.forename: Qingxia
authors.initials: Q
authors.lastname: Chen
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Zhu
authors.forename: John V
authors.initials: JV
authors.lastname: Williams
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Edwards
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007252:Influenza Vaccines / Q000008:administration & dosage*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D009666:Nose / Q000821:virology; D009975:Orthomyxoviridae / Q000302:isolation & purification; D010614:Pharynx / Q000821:virology; D015995:Prevalence; D011446:Prospective Studies; D012367:RNA, Viral / Q000235:genetics / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014611:Vaccination / Q000706:statistics & numerical data; D014773:Virology / Q000379:methods
chemical_list: D007252:Influenza Vaccines; D012367:RNA, Viral