Effectiveness of adjuvanted seasonal influenza vaccines (Inflexal V^®and Fluad^®) in preventing hospitalization for influenza and pneumonia in the elderly

Abstract

Annual vaccination is the main mean of preventing influenza in the elderly. In order to evaluate the effectiveness of the adjuvanted seasonal influenza vaccines available in Italy in preventing hospitalization for influenza and pneumonia, a matched case-control study was performed in elderly subjects during the 2010–2011 season in Genoa (Italy). Cases and controls were matched in a 1:1 ratio according to gender, age, socio-economic status and type of influenza vaccine. Vaccine effectiveness was calculated as IVE = [(1-OR)x100] and crude odds ratios were estimated through conditional logistic regression models. Adjusted odds ratios were estimated through multivariable logistic models. In the study area, influenza activity was moderate in the 2010–2011 season, with optimal matching between circulating viruses and vaccine strains. We recruited 187 case-control pairs; 46.5% of cases and 79.1% of controls had been vaccinated. The adjuvanted influenza vaccines (Fluad® considered together with Inflexal V®) were associated with a significant reduction in the risk of hospitalization, their effectiveness being 94.8% (CI 77.1–98.8). Adjusted vaccine effectiveness was 95.2% (CI 62.8–99.4) and 87.8 (CI 0.0–98.9) for Inflexal V® and Fluad®, respectively. Both adjuvanted vaccines proved effective, although the results displayed statistical significance only for Inflexal V® (p = 0.004), while for Fluad® statistical significance was not reached (p = 0.09). Our study is the first to provide information on the effectiveness of Inflexal V® in terms of reducing hospitalizations for influenza or pneumonia in the elderly, and demonstrates that this vaccine yields a high degree of protection and that its use would generate considerable saving for the National Health Service.

Selection of an adjuvant for seasonal influenza vaccine in elderly people: modelling immunogenicity from a randomized trial

“…The oil-in-water adjuvant MF59™ contains polysorbate 80, sorbitan trioleate, trisodium citrate dehydrate, citric acid monohydrate, and has been shown to enhance immune responses to seasonal influenza vaccine compared with non-adjuvanted vaccine [10,38]. An MF59™-adjuvanted influenza vaccine (Fluad™) is licensed and widely used, and has been shown to significantly reduce hospitalization for influenza and pneumonia compared with non-adjuvanted vaccine in elderly people [39]. However, there have been no prospective, randomized clinical trials of vaccine efficacy of this formulation in people aged ≥65 years [10].…”

Seasonal influenza immunisation: Strategies for older adults

“…This reduction was achieved despite the preferential use of aTIV in older and more frail individuals. Smaller Italian studies have confirmed the effectiveness of aTIV in elderly individuals in long‐term care, and those living in the community . A study in Canada compared the effectiveness of aTIV with TIV to prevent laboratory‐confirmed influenza in ≥65‐year‐olds, specifically selecting half the participants to be ≥85 years of age, and included those living in care or in the community .…”

Fluad®-MF59®-Adjuvanted Influenza Vaccine in Older Adults

“…A case-control study conducted in Italy during the 2010-11 season compared patients hospitalized with influenza or pneumonia and matched non-hospitalized persons and found a non-significant VE for IIVa3 of 87.8% (0-98.9%) (34). However, these studies relied on administrative databases in which cases would not always have been laboratory-confirmed, which has been identified as a methodological shortcoming of administrative data.…”