Safety and Immunogenicity of A Quadrivalent Meningococcal Conjugate Vaccine (Menacyw-Tt) Administered in Healthy Meningococcal Vaccine-Naïve Children (2-9 Years)

Abstract Background MenACYW-TT is an investigational quadrivalent meningococcal conjugate vaccine that contains tetanus toxoid as carrier protein. The vaccine is intended for global use in individuals 6 weeks of age and older. We evaluated the safety and immunogenicity of MenACYW-TT compared with a licensed quadrivalent conjugate meningococcal vaccine (MenACWY-CRM [Menveo®]) in US children 2–9 years of age. Methods In a modified double-blind Phase III study (NCT03077438), 1000 children were randomized to receive one dose of either MenACYW-TT vaccine or MenACWY-CRM vaccine. Serum bactericidal assays with human (hSBA) and baby rabbit (rSBA) complement were used to measure antibodies against representative meningococcal serogroup strains at baseline and 30 days after vaccination. Safety data were collected up to 6 months post-vaccination. Results Non-inferiority of immune responses for all four serogroups, based on percentages of participants achieving hSBA vaccine seroresponse, was demonstrated for MenACYW-TT compared with MenACWY-CRM at Day 30 compared with baseline. The proportions of individuals with hSBA titers ≥ 1:8 following MenACYW-TT administration were higher than those after MenACWY-CRM administration for all four serogroups (A: 86.4% vs 79.3%; C: 97.8% vs 67.1%; W: 94.8% vs 86.3%; Y: 98.5% vs 90.8%). Similar results were observed in two age substrata (2 to 5 years and 6 to 9 years). Percentages of participants with post-vaccination rSBA titers ≥ 1:128 were comparable between both groups. The safety profiles of MenACYW-TT and MenACWY-CRM were comparable. Reactogenicity at the MenACYW-TT injection site was lower than at the MenACWY-CRM injection site. There were no immediate adverse events (AEs), no AEs leading to study discontinuation, and no vaccine-related serious adverse events reported in the study. Conclusion MenACYW-TT vaccine was well tolerated and demonstrated a non-inferior immune response compared with that for the licensed MenACWY-CRM vaccine when administered as a single dose to meningococcal vaccine-naïve children. Disclosures All authors: No reported disclosures.