Humoral and cellular immune responses to split-virion H5N1 influenza vaccine in young and elderly adults

We evaluated the humoral and cellular immunogenicity of adjuvanted and non-adjuvanted H5N1 influenza vaccine in two groups of 300 adults: aged 18-60 and >60 years in a randomized, open-label, uncontrolled phase 2 trial. Participants received two injections (D0, D21) of 7.5 mu g hemagglutinin without adjuvant or 30 mu g with aluminum hydroxide adjuvant. Antibody responses and cytokine secretion were assessed before and after vaccination. Excluding the 6/300 non-elderly and 47/300 elderly participants with pre-existing antibodies, geometric mean titers (dil(-1)) on D42 were higher with 30 mu g+Ad and were comparable between age groups. Participants with pre-existing antibodies responded strongly to the first vaccination (GMTs in the range 147-228 on D21). Vaccination increased both Th1 and Th2 T-cell responses. The predominantly Th1 profile observed before vaccination was unaffected by vaccination. H5N1 influenza vaccine is no less immunogenic in elderly adults than in younger adults and, due to a higher proportion non-naive elderly, immunogenicity was higher in this latter group. (C) 2009 Elsevier Ltd. All rights reserved.