Safety and Immunogenicity of a Quadrivalent Meningococcal Conjugate Vaccine in Healthy Meningococcal-Naïve Children 2–9 Years of Age: A Phase III, Randomized Study

Background: Invasive meningococcal disease is a major cause of meningitis in children. An investigational meningococcal (serogroups A, C, Y, and W) tetanus toxoid conjugate vaccine (MenACYW-TT) could offer protection against invasive meningococcal disease in this population. This phase III study assessed the immunogenicity and safety of MenACYW-TT in children compared with a licensed quadrivalent meningococcal vaccine conjugated with diphtheria protein CRM197 (MenACWY-CRM). Methods: Healthy children 2–9 years of age in the United States, including Puerto Rico, were randomized (1:1) to receive MenACYW-TT (n = 499) or MenACWY-CRM (n = 501) (NCT03077438). Meningococcal antibody titers to the 4 vaccine serogroups were measured using a serum bactericidal antibody assay with human complement (hSBA) before and at day 30 after vaccination. Noninferiority between the vaccine groups was assessed by comparing seroresponse rates (postvaccination titers ≥1:16 when prevaccination titers were <1:8, or ≥4-fold increase if prevaccination titers were ≥1:8) to the 4 serogroups at day 30. Safety was monitored. Results: The proportion of participants achieving seroresponse at day 30 in the MenACYW-TT group was noninferior to the MenACWY-CRM group (A: 55.4% vs. 47.8%; C: 95.2% vs. 47.8%; W: 78.8% vs. 64.1%; Y: 91.5% vs. 79.3%, respectively). Geometric mean titers for serogroups C, W, and Y were higher with MenACYW-TT than for MenACWY-CRM. Both vaccines were well-tolerated and had similar safety profiles. Conclusions: MenACYW-TT was well-tolerated in children and achieved noninferior immune responses to MenACWY-CRM against each of the 4 vaccine serogroups.