Effect of Previous-Year Vaccination on the Efficacy, Immunogenicity, and Safety of High-Dose Inactivated Influenza Vaccine in Older Adults
Clinical Infectious Diseases May 1, 2016 V.62 N.9 P.1092-1099
Carlos A. DiazGranados, Andrew J. Dunning, Corwin A. Robertson, H. Keipp Talbot, Victoria Landolfi, and David P. Greenberg
1Sanofi Pasteur, Swiftwater, Pennsylvania
2Vanderbilt University Medical Center, Nashville, Tennessee
3Department of Pediatrics, University of Pittsburgh School of Medicine, Pennsylvania
High-dose inactivated influenza vaccine (IIV-HD) is an alternative to the standard-dose inactivated influenza vaccine (IIV-SD) in the United States for influenza prevention in older adults. IIV-HD improved efficacy relative to IIV-SD in a randomized controlled trial. Recent observational studies suggest that previous influenza vaccination may influence the immunogenicity and effectiveness of current-season vaccination.
The original study was a double-blind, randomized trial comparing IIV-HD to IIV-SD in adults aged ≥65 years over 2 influenza seasons. A subset of year 1 (Y1) participants reenrolled in year 2 (Y2), receiving vaccine by random assignment in both years. We evaluated the effect of Y1 vaccination on Y2 relative vaccine efficacy (VE), immunogenicity (hemagglutination inhibition [HAI] titers), and safety among reenrolled participants.
Of 14 500 Y1 participants, 7643 reenrolled in Y2. Relative to participants who received IIV-SD both seasons, VE was higher for IIV-HD vaccinees in Y2 (28.3% overall; 25.1% for Y1 IIV-HD, Y2 IIV-HD; and 31.6% for Y1 IIV-SD, Y2 IIV-HD). In multivariate logistic regression models, Y1 vaccine was not a significant modifier of Y2 VE (P = .43), whereas Y2 IIV-HD remained significantly associated with lower influenza risk (P = .043). Compared to administration of IIV-SD in both years, postvaccination HAI titers were significantly higher for patterns that included IIV-HD in Y2. No safety concerns were raised with IIV-HD revaccination.
IIV-HD is likely to provide clinical benefit over IIV-SD irrespective of previous-season vaccination with IIV-HD or IIV-SD. IIV-HD consistently improved immune responses, and no safety concerns emerged in the context of IIV-HD revaccination.
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