Safety and immunogenicity of three doses of a Neisseria meningitidis A+C diphtheria conjugate vaccine in infants from Niger

Background, High rates of endemic disease and recurrent epidemics of serogr oup A and C meningococcal meningitis continue to occur in sub-Saharan Afric a. A meningococcal A + C polysaccharide diphtheria-toxoid-conjugated vaccin e may address this issue. Methods, In Niger three doses of a bivalent meningococcal A + C diphtheria- toxoid-conjugated vaccine (MenD), containing 1, 4 or 16 mu g of each polysa ccharide per dose, administered at 6, 10 and 14 weeks of age, were compared with Haemophilus influenzae type b-tetanus toxoid-conjugated (PRP-T) vacci ne given with the same schedule or with a meningococcal A + C polysaccharid e vaccine (MenPS) given at 10 and 14 weeks of age. One blood sample was tak en at the time of enrollment (6 weeks of age) and another was taken 4 weeks after the primary series. Results, All doses of MenD were well-tolerated. After the primary series a higher proportion of infants had detectable serum bactericidal activity aga inst serogroup A for each dose of MenD (from 94% to 100%) than for MenPS (3 1%) or H. influenzae type b-tetanus toxoid-conjugated vaccine (18.9%); P le ss than or equal to 0.05, Significant differences were also observed for se rogroup C MenD 4 pg or MenD 16 mu g (100%) vs. MenPS (69.7%) or Haemophilus influenzae type b-tetanus toxoid-conjugated vaccine (24.3%); P less than o r equal to 0.05, When MenPS vaccine was given to Ii-month-old children, the immune response measured by both enzyme-linked immunosorbent assay and ser um bactericidal assay was greater in those previously immunized with MenD t han in those immunized with MenPS vaccine. Conclusion. MenD was safe among infants in Niger, and immunization led to s ignificantly greater functional antibody activity than with MenPS, The 4-mu g dose of MenD for both the A and C serogroups has been selected for furth er studies.