Immunogenicity and safety of three commercial influenza vaccines in institutionalized elderly

Influenza is a leading cause of morbidity and mortality in elderly people. This prospective, observed-blind, randomized, multicenter trial compares th e immunogenicity and safety of three influenza vaccines in a sample of 635 elderly residents of four nursing homes in Milano (Italy). All vaccines wer e well tolerated: no serious adverse events were recorded, and a small numb er (9 subjects) of local and systemic reactions were observed. Twenty-nine oropharyngeal swabs were taken during the season from ILI (influenza-like i llness) patients, none of whom was positive for influenza and other respira tory viruses. Immune genicity was evaluated in a subgroup of 111 subjects w ith blood samples obtained just before vaccination and after 4 and 12 weeks . The adjuvanted vaccines, subunit vaccine with MF59 (a-SUV) and virosome s ubunit vaccine (v-SUV), induced a higher antibody response than whole virus vaccine (WW). There was no significant difference between groups that rece ived a-SUV and v-SUV, but the a-SUV group had higher values of geometric me an titres than the v-SUV group for H1N1 and B influenza strains. These find ings suggest that influenza vaccination is effective, and they underscore t he importance of vaccination programs for institutionalized elderly. Furthe r studies are needed to compare other adjuvanted vaccines in order to defin e their different properties.