• Qingxia Chen, Marie R Griffin, Hui Nian, Yuwei Zhu, John V Williams, Kathryn M Edwards, and H Keipp Talbot.
• Department of Biostatistics Department of Biomedical Informatics, Vanderbilt University Medical Center.
• J. Infect. Dis. 2015 Apr 1;211(7):1045-50.

BackgroundThere are few estimates of effectiveness influenza vaccine in preventing serious outcomes due to influenza in older adults.MethodsAdults 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.ResultsA 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.ConclusionsInfluenza vaccine was moderately effective in preventing influenza-associated medical care visits in older adults.© The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

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