Immunogenicity and Safety of a Quadrivalent Meningococcal Tetanus Toxoid-Conjugate Vaccine (MenACYW-TT) Versus a Licensed Quadrivalent Meningococcal Tetanus Toxoid-Conjugate Vaccine in Meningococcal Vaccine-Naïve and Meningococcal C Conjugate Vaccine-Primed Toddlers: a Phase III Randomized Study

Vaccination remains the best strategy to reduce invasive meningococcal disease. This study evaluated an investigational tetanus toxoid-conjugate quadrivalent meningococcal vaccine (MenACYW-TT) vs. a licensed tetanus toxoid-conjugate quadrivalent meningococcal vaccine (MCV4-TT) (NCT02955797). Healthy toddlers aged 12-23 months were included if they were either meningococcal vaccine-naive or MenC conjugate (MCC) vaccine-primed (≥1 dose of MCC prior to 12 months of age). Vaccine-naive participants were randomised 1:1 to either MenACYW-TT (n = 306) or MCV4-TT (n = 306). MCC-primed participants were randomised 2:1 to MenACYW-TT (n = 203) or MCV4-TT (n = 103). Antibody titres against each of the four meningococcal serogroups were measured by serum bactericidal antibody assay using the human complement. The co-primary objectives of this study were to demonstrate the non-inferiority of MenACYW-TT to MCV4-TT in terms of seroprotection (titres ≥1:8) at Day 30 in both vaccine-naive and all participants (vaccine-naive and MCC-primed groups pooled). The immune response for all four serogroups to MenACYW-TT was non-inferior to MCV4-TT in vaccine-naive participants (seroprotection: range 83.6-99.3% and 81.4-91.6%, respectively) and all participants (seroprotection: range 83.6-99.3% and 81.4-98.0%, respectively). The safety profiles of both vaccines were comparable. MenACYW-TT was well-tolerated and demonstrated non-inferior immunogenicity when administered to MCC vaccine-primed and vaccine-naive toddlers.