Immunogenicity and safety of monovalent P1.7h,4 meningococcal outer membrane vesicle vaccine in toddlers:: comparison of two vaccination schedules and two vaccine formulations

The safety and immunogenicity of two PorA-based meningococcal outer membrane vesicle (OMV) vaccines against the P1.4 serosubtype adsorbed with AlPO4 or Al(OH)(3) were studied in 134 toddlers. Vaccinations were given three times with an interval of 3-6 weeks or twice with an interval of 6-10 weeks. A vaccination was repeated after 20-40 weeks. Pre- and post-immunization sera were tested for bactericidal activity against an isogenic strain expressing P1.7(h),4 PorA. Both meningococcal OMV vaccines were well tolerated. The percentage of children with a fourfold increase in bactericidal activity was 96% (AlPO4-adjuvated vaccine/2 + 1 schedule), 100% (AlPO4-adjuvated vaccine/3 + 1, schedule), 93% (Al(OH)(3)-adjuvated vaccine/2 + 1 schedule) and 97% (Al(OH)(3)-adjuvated vaccine/3 + 1 schedule). Adsorption with AlPO4 makes the OMV vaccine more immunogenic than adsorption with AI(OH)(3). Bactericidal activity was highest after the 3 + 1 schedule, although the response shortly after the primary series was higher in the two-dose priming group. (C) 2000 Elsevier Science Ltd. All rights reserved.