• Carlos A DiazGranados, Corwin A Robertson, H Keipp Talbot, Victoria Landolfi, Andrew J Dunning, and David P Greenberg.
• Sanofi Pasteur, 1 Discovery Drive, Swiftwater, PA 18370, USA. Electronic address: carlos.diazgranados@sanofipasteur.com.
• Vaccine. 2015 Sep 11; 33 (38): 4988-93.

BackgroundA recent study showed that a high-dose inactivated influenza vaccine (IIV-HD) was 24.2% more efficacious than a standard-dose inactivated influenza vaccine (IIV-SD) in preventing laboratory-confirmed symptomatic influenza in adults ≥65 years. Here we evaluate the effectiveness of IIV-HD compared to IIV-SD in preventing serious illnesses considered potential sequelae or complications of influenza infection.MethodsThe original study was a double-blind, randomized, active-controlled, multicenter trial. Participants were adults ≥65 years randomized to receive IIV-HD or IIV-SD, and followed for 6-8 months post-vaccination for the occurrence of influenza and serious adverse events (SAEs). SAEs were events: leading to death or hospitalization (or its prolongation); considered life-threatening or medically important; or resulting in disability. For the present analysis, reported SAEs were classified as possibly related to influenza by three blinded physicians and rates per 1000 participant-seasons were calculated. Relative vaccine effectiveness (rVE) was estimated as (1-Rate Ratio)×100.Results31,989 participants were enrolled, with 15,991 and 15,998 randomized to receive IIV-HD and IIV-SD, respectively. IIV-HD was significantly more effective than IIV-SD in preventing SAEs possibly related to influenza overall (rVE, 17.7%; 95% confidence interval [CI], 6.6-27.4%) and serious pneumonia (rVE, 39.8%; 95% CI, 19.3-55.1%). Borderline significance was observed for the efficacy of IIV-HD relative to IIV-SD for the prevention of all-cause hospitalizations (rVE, 6.9%; 95% CI, 0.5-12.8%).ConclusionsCompared to IIV-SD, IIV-HD reduced the risk of SAEs possibly related to influenza. The observed relative effectiveness against serious pneumonia is particularly noteworthy considering the burden of influenza and pneumonia in older adults.Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

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