HealthDay News — A high-dose, trivalent, inactivated influenza vaccine (IIV3-HD) is associated with improved protection for seniors against laboratory-confirmed influenza infection compared with standard-dose vaccine (IIV3-SD), according to research published in the New England Journal of Medicine.

To compare IIV3-HD with II3-SD, Carlos A. DiazGranados, MD, of Sanofi Pasteur in Swiftwater, Pa., and colleagues conducted a phase IIIb-IV randomized double-blind trial. Participants from 126 research centers, aged 65 years and older, were randomly assigned IIV3-HD (n=15,991) or IIV3-SD (n=15,998 participants).

Of the patients, 1.4% in the IIV3-HD group and 1.9% in the IIV3-SD group had laboratory-confirmed flu caused by any viral type or subtype that was associated with a protocol-defined flu-like illness (relative efficacy, 24.2%). 

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During the safety surveillance period, 8.3% of participants in the IIV3-HD group and 9.0% in the IIV3-SD group had at least one serious adverse event (relative risk, 0.92; 95% CI: 0.85-0.99). In the IIV3-HD group, hemagglutination-inhibition titers and seroprotection rates were significantly higher after vaccination.

“Among persons 65 years of age or older, IIV3-HD induced significantly higher antibody responses and provided better protection against laboratory-confirmed influenza illness than did IIV3-SD,” concluded the researchers.


  1. DiazGranados C et al. New England Journal of Medicine. 2014; doi: 10.1056/NEJMoa1315727

Disclosures: The study was funded by Sanofi Pasteur.