• H Keipp Talbot, Marie R Griffin, Qingxia Chen, Yuwei Zhu, John V Williams, and Kathryn M Edwards.
• Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA. keipp.talbot@vanderbilt.edu
• J. Infect. Dis. 2011 Feb 15;203(4):500-8.

BackgroundCurrent evidence supporting the effectiveness of influenza vaccine in preventing hospitalizations in older adults is insufficient.MethodsDuring 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.ResultsOverall, 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%).ConclusionOverall, 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.

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