Open, randomized study to compare the immunogenicity and reactogenicity of an influenza split vaccine with an MF59-adjuvanted subunit vaccine and a virosome-based subunit vaccine in elderly

Background: An open, randomized, multicenter study was carded out in elderly to compare the immunogenicity and reactogenicity of a conventional influenza split vaccine (SpV) with an MF59-adjuvanted subunit vaccine (aSuV) and a virosome-based subunit vaccine (vSuV) since earlier studies reported better immunogenicity for adjuvanted and virosome-based vaccines. Patients and Methods: A total of 840 subjects, aged 60 years or more, who had not been vaccinated or diagnosed with influenza in the preceding season were investigated. Hemagglutination-inhibition antibody titers were measured, and signs and symptoms recorded. Results: The three vaccines exceeded EU efficacy requirements for subjects aged older than 60 years and seroprotective levels (titers >1:40) were equally maintained with the three vaccines during 8 months post vaccination. SpV was as immunogenic as aSuV for the A/H3N2 strain (p<0.0001) and significantly more immunogenic than aSuV for A/H1N1 strain (p=0.0006). SpV was as immunogenic as vSuV for all three strains and significantly more immunogenic than vSuV for the A/H1N1 strain (p<0.0001). In terms of reactogenicity, aSuV showed a higher rate of solicited local signs and symptoms than SpV (p=0.021) and vSuV (p=0.046), respectively. Incidence of solicited general symptoms was comparable on all treatments. No serious adverse event related to vaccination was reported. Conclusion: These findings suggest that all three vaccines are highly immunogenic with an acceptable reactogenicity profile and that they are appropriate for use in elderly.