Safety and Immunogenicity of a Quadrivalent Meningococcal Polysaccharide Diphtheria Toxoid Conjugate Vaccine in Infants and Toddlers: Three Multicenter Phase III Studies

Background: Quadrivalent meningococcal conjugate vaccine (Menactra [MenACWY-D]), was licensed in the United States in 2005 to prevent meningococcal disease in adolescents and adults. The license was extended to children aged 2-10 years in 2007 and extended again in 2011 to infants aged 9 months and older based, in part, on results from 3 phase III studies presented herein. Methods: The safety and immunogenicity of 2 doses of MenACWY-D was assessed in study-eligible children: dose 1 was administered at 9 months of age and dose 2 was administered 3 months later with or without routine childhood vaccines. Results: Thirty days after vaccination, protective serum bactericidal assay-human complement titers >= 1:8 for meningococcal serogroups A, C, Y and W-135 were achieved by 86-100% of children receiving 2 doses of MenACWY-D. When MenACWY-D was concomitantly administered with measles, mumps, rubella and varicella or heptavalent pneumococcal conjugate vaccine, 81-98% of participants achieved protective responses (serum bactericidal assay-human complement titers >= 1:8 for all serogroups). All seroprotection rates were >91% when the protective titer was defined as serum bactericidal assay-human complement >= 1:4. MenACWY-D did not interfere with measles, mumps, rubella or varicella vaccine responses (98-100% achieved protective titers). When heptavalent pneumococcal conjugate vaccine was given concomitantly with MenACWY-D, antipneumococcal antibody levels, although decreased, were protective for all serotypes by enzyme-linked immunosorbent assay (98-100% >= 0.35 mu g/mL) and opsonophagocytic assay (99-100% >= 1:8). Adverse events were generally mild and similar across groups. Serious adverse events were uncommon. Conclusions: MenACWY-D was safe and immunogenic when given in 2 doses to infants and toddlers; this vaccine can be given with other common childhood immunizations.