Phase II, randomized, open, controlled study of AS03-adjuvanted H5N1 pre-pandemic influenza vaccine in children aged 3 to 9 years: follow-up of safety and immunogenicity persistence at 24 months post-vaccination.

BACKGROUND: An AS03-adjuvanted H5N1 influenza vaccine elicited broad and persistent immune responses with an acceptable safety profile up to 6 months following the first vaccination in children aged 3-9 years. METHODS: In this follow-up of the Phase II study, we report immunogenicity persistence and safety at 24 months post-vaccination in children aged 3-9 years. The randomized, open-label study assessed two doses of H5N1 A/Vietnam/1194/2004 influenza vaccine (1·9 µg or 3·75 µg hemagglutinin antigen) formulated with AS03A or AS03B (11·89 mg or 5·93 mg tocopherol, respectively). Control groups received seasonal trivalent influenza vaccine. Safety was assessed prospectively and included potential immune-mediated diseases (pIMDs). Immunogenicity was assessed by hemagglutination-inhibition assay 12 and 24 months after vaccination; cross-reactivity and cell-mediated responses were also assessed. (NCT00502593). RESULTS: The safety population included 405 children. Over 24 months, five events fulfilled the criteria for pIMDs, of which four occurred in H5N1 vaccine recipients, including uveitis (n = 1) and autoimmune hepatitis (n = 1), which were considered to be vaccine-related. Overall, safety profiles of the vaccines were clinically acceptable. Humoral immune responses at 12 and 24 months were reduced versus those observed after the second dose of vaccine, although still within the range of those observed after the first dose. Persistence of cell-mediated immunity was strong, and CD4(+) T cells with a TH 1 profile were observed. CONCLUSIONS: Two doses of an AS03-adjuvanted H5N1 influenza vaccine in children showed low but persistent humoral immune responses and a strong persistence of cell-mediated immunity, with clinically acceptable safety profiles up to 24 months following first vaccination.

Antibody persistence 12 months after a booster dose of meningococcal-C conjugated vaccine in the second year of life.

We report on the results of the 12-month follow-up of children aged 14 to 18 months who received primary and booster vaccinations with either a meningococcal-C vaccine conjugated to tetanus toxoid or CRM197. Seroprotection (92.8%) and geometric mean titers/serum bactericidal activity (410.5; 95% CI: 273.4-616.3) were higher in children receiving the meningococcal serogroup C tetanus toxoid conjugate, compared with 61.5% and serum bactericidal antibody geometric mean titer of 45.1 (95% CI: 28.5-71.3) when MenC-CRM197 conjugate was used.