• Carlos A DiazGranados, William Saway, James Gouaux, Mira Baron, Jeffrey Baker, Martine Denis, Emilia Jordanov, Victoria Landolfi, and Eddy Yau.
• Sanofi Pasteur, Inc., Swiftwater, PA, USA. Electronic address: carlos.diazgranados@sanofipasteur.com.
• Vaccine. 2015 Dec 16; 33 (51): 7188-7193.

BackgroundIndividuals 50-64 years of age have reduced immune responses to influenza vaccines. The current study examined whether a high-dose inactivated trivalent influenza vaccine (IIV3-HD) might improve immune responses over a standard-dose inactivated influenza vaccine (IIV3-SD) in this age group.MethodsThis was a multicenter, observer-blinded, randomized, active-controlled phase II trial. Adults 50-64 years of age were randomized 1:1 to receive IIV3-HD or IIV3-SD. Hemagglutination inhibition titers were measured before and 28 days after vaccination. Reactogenicity was recorded for 7 days after vaccination and adverse events for 28 days.Results148 participants received IIV3-HD and 152 received IIV3-SD. For all vaccine strains, day 28 geometric mean hemagglutination inhibition titers were significantly higher in the IIV3-HD group than in the IIV3-SD group (geometric mean titer ratio [95% confidence interval (CI)]=1.43 [1.04-1.97] for A/H1N1, 1.65 [1.21-2.25] for A/H3N2, and 1.60 [1.23-2.08] for B). Seroconversion rates were significantly higher in the IIV3-HD group than in the IIV3-SD group for strains A/H3N2 and B but not A/H1N1 (difference [95% CI]=13.5% [4.76-22.0] for A/H3N2, 23.1% [11.7-33.6] for B, and -0.2% [-9.66 to 9.18] for A/H1N1). The post-vaccination seroprotection rate was significantly higher in the IIV3-HD group than in the IIV3-SD group for strain B but not for strains A/H1N1 or A/H3N2 (difference=9.1% [2.95-15.7] for B, 2.0% [-0.907 to 5.68] for A/H1N1, and 0.6% [-3.14 to 4.43] for A/H3N2). Reactogenicity was higher in the IIV3-HD group than in the IIV3-SD group, but reactions were mostly of low intensity, transient, and self-limited. Rates of unsolicited adverse events were similar between groups. No serious AEs, AEs leading to early withdrawal, or deaths were reported.ConclusionsThe study suggests that in adults 50-64 years of age, IIV3-HD may improve immunogenicity compared to IIV3-SD while maintaining an acceptable safety profile.Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

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