A Safety and Immunogenicity Study of a Single Dose of a Meningococcal (Groups A, C, W, and Y) Polysaccharide Diphtheria Toxoid Conjugate Vaccine (MEN-ACWY-D) in Healthy Japanese Participants

: Meningococcal disease can cause significant disability and mortality. The quadrivalent meningococcal polysaccharide diphtheria toxoid conjugate vaccine (Men-ACWY-D) protects against invasive meningococcal disease caused by serogroups A, C, W, and Y. This phase III, open-label, single-arm, multicenter study evaluated the safety and immunogenicity of a single vaccine dose in healthy Japanese adults. The study enrolled 200 participants between 2 and 55 years of age. Immunogenicity was assessed by quantifying the seroprotection rates (the proportion of participants with antibody titers ≥ 1:128 against the capsular polysaccharide from all 4 serogroups measured 28 days after vaccination). Safety endpoints included occurrence, nature, time to onset, duration, intensity, relationship to vaccination, and outcome of solicited and unsolicited adverse events (AEs) and serious AEs (SAEs). Participants included 194 adults, 2 adolescents, and 4 children. Among adults, the seroprotection rates for serogroups A, C, W, and Y were 91.2%, 80.2%, 89.1%, and 93.8%, respectively. Seroconversion rates (the proportion of participants with pre-vaccination titers of < 1:4 and a ≥ 4-fold rise from baseline) were 87.3%, 83.0%, 94.4%, and 96.4%, respectively. No immediate AEs, adverse reactions, SAEs, or deaths were reported for any age group. Men-ACWY-D is well tolerated and immunogenic, eliciting antibodies against capsular polysaccharides from all 4 serogroups in Japanese adults.