Meningococcal disease poses a significant health threat to military personnel due to their close living quarters and potential deployments to endemic or hyperendemic areas. Therefore, vaccination of this population is essential for prevention. MenACYW-TT (MenQuadfi®, Sanofi), a quadrivalent meningococcal tetanus toxoid conjugate vaccine, has demonstrated immunogenicity and safety in persons 6 weeks of age and older. In a Phase 3, blinded, randomized clinical trial (ClinicalTrials.gov identifier NCT02842853), 3,344 meningococcal vaccine–naïve individuals aged 10–55 were randomly assigned to receive MenACYW-TT (from one of three lots) or a licensed quadrivalent meningococcal diphtheria toxoid conjugate vaccine (MenACWY-D; Menactra®, Sanofi). The study aimed to demonstrate lot-to-lot consistency of MenACYW-TT and non-inferiority of the immune response of MenACYW-TT vs MenACWY-D based on seroresponse measured 30 days after vaccination. Antibody levels were assessed with a serum bactericidal assay using human complement (hSBA). All three MenACYW-TT lots met criteria for lot-to-lot consistency and pooled data demonstrated non-inferior immunogenicity across all serogroups compared with MenACWY-D; seroresponse rates were 74% vs 55% for serogroup A; 89% vs 48% for serogroup C; 80% vs 61% for serogroup W; and 91% vs 73% for serogroup Y). Both vaccines were well tolerated with comparable safety profiles, and no safety concerns were identified. MenACYW-TT met both co-primary endpoints, confirming consistent immunogenicity and an acceptable safety profile in adolescents and adults. Data specifically addressing immunogenicity and safety of meningococcal vaccines the in military-age population are limited. A post-hoc analysis of the phase 3 study described above was conducted. The analysis was confined to young adults aged 17– 29 years. The primary outcome of interest was the percentage of participants achieving a non-inferior seroresponse to each serogroup 30 days after vaccination as measured by hSBA. Safety outcomes included the occurrence of solicited acute reactions (ARs) within 7 days after vaccination, unsolicited adverse events (AEs) within 30 days after vaccination, and serious adverse events within 6 months after vaccination. A total of 364 participants were included in the post-hoc analysis; of these, 303 received MenACYWTT and 61 received MenACWY-D. MenACYW-TT induced non inferior immune responses compared to MenACYW-D, as assessed by seroresponse rates: 77.9% vs 65.6% for serogroup A, 91.7% vs 65.6% for serogroup C, 93.7% vs 83.6% for serogroup Y, and 84.2% vs 70.5% for serogroup W. Rates of seroprotection (defined as an hSBA titer ≥ 1:8) for MenACYW-TT vs MenACWY-D, respectively, were 95.7% vs 91.8% for serogroup A, 98.0% vs 85.2% for serogroup C, 99.7% vs 93.4% for serogroup Y, and 99.0% vs 91.8% for serogroup W. MenACYW-TT had an acceptable safety profile. Rates of solicited injection site and solicited systemic reactions were comparable between the two vaccine groups. No participants had an adverse event leading to study discontinuation and no deaths were reported. These findings suggest that MenACYWTT is well tolerated and effective against meningococcal disease in young adults, supporting its use in military-age populations.