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.