title: Influenza vaccine prevents medically attended influenza-associated acute respiratory illness in adults aged ≥50 years.
abstract: BACKGROUND
  There are few estimates of effectiveness influenza vaccine in preventing serious outcomes due to influenza in older adults.
  
  
  METHODS
  Adults aged ≥50 years who sought medical care for acute respiratory illness were enrolled. A nose/throat swab was tested for influenza virus by reverse transcription-polymerase chain reaction. Clinical and demographic data were collected, including verification of receipt of trivalent inactivated influenza vaccination (IIV-3). Adjusted odds ratios were estimated by multivariable logistic regression models with an L1 penalty on all covariates except vaccination status.
  
  
  RESULTS
  A total of 1047 subjects were enrolled from November through April during 5 influenza seasons during 2006-2012, excluding the 2009-2010 season. Of those enrolled, 927 (88%) had complete influenza virus testing, vaccination status, and demographic data obtained. Of 86 (9.3%) influenza virus-positive patients, 47 (55%) were vaccinated. Of 841 influenza virus-negative patients, 646 (76.8%) were vaccinated. Over 5 influenza seasons, IIV-3 was 58.4% effective (95% confidence interval [CI], 37.0%-75.6%) for the prevention of medically attended laboratory-confirmed influenza illness in adults aged ≥50 years and 58.4% effective (95% CI, 7.9%-81.1%) in adults aged ≥65 years.
  
  
  CONCLUSIONS
  Influenza vaccine was moderately effective in preventing influenza-associated medical care visits in older adults.
authors.affiliation: Department of Biostatistics Department of Biomedical Informatics, Vanderbilt University Medical Center.
authors.forename: Qingxia
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Preventive Medicine Department of Medicine Department of Mid-South Geriatric Research Education and Clinical Center Department of Clinical Research Center of Excellence, VA Tennessee Valley Health Care System, Nashville, Tennessee.
authors.forename: Marie R
authors.initials: MR
authors.lastname: Griffin
authors.affiliation: Department of Biostatistics.
authors.forename: Hui
authors.initials: H
authors.lastname: Nian
authors.affiliation: Department of Biostatistics.
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Department of Pediatrics Department of Microbiology and Immunology.
authors.forename: John V
authors.initials: JV
authors.lastname: Williams
authors.affiliation: Department of Pediatrics.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Edwards
authors.affiliation: Department of Medicine.
authors.forename: H Keipp
authors.initials: HK
authors.lastname: Talbot
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006760:Hospitalization; D006801:Humans; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control* / Q000821:virology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009666:Nose / Q000821:virology; D009975:Orthomyxoviridae / Q000276:immunology* / Q000302:isolation & purification; D010614:Pharynx / Q000821:virology; D011446:Prospective Studies; D012621:Seasons; D014611:Vaccination; D015164:Vaccines, Inactivated
chemical_list: D007252:Influenza Vaccines; D015164:Vaccines, Inactivated
keywords: control-negative; elderly; influenza vaccine effectiveness; older adults