Immunogenicity
MenACYW-TT-
BLOOD, SECONDARY
Blood samples for immunogenicity analyses were obtained prior to (Day 0) and 30 (+14) days after booster vaccination. A subset of the first 50 participants enrolled into groups 1 (MenACYW-TT primed, MenACYW-TT booster) and 2 (MCV4-CRM primed, MenACYW-TT booster) provided additional post-vaccination samples on Day 6 (±1 day).Functional antibody titers against meningococcal serogroups A, C, W and Y were measured by a serum bactericidal antibodies assay using human complement (hSBA; Global Clinical Immunology, Sanofi, Swiftwater, PA), as described previously.The primary immunogenicity endpoints of this study were vaccine seroresponse rates against meningococcal serogroups (A, C, W and Y) following a booster dose of MenACYW-TT in participants primed with MenACYW-TT 3–6 years previously, based on hSBA titers pre-booster and 30 days post booster. The secondary immunogenicity endpoints were hSBA seroresponse and seroprotection rates and geometric mean titers (GMTs) against serogroups A, C, W and Y in MenACYW-TT- or MCV4-CRM-primed participants, pre- (to evaluate persistence of immune response) and 30 days post-MenACYW-TT booster and, for a subset of participants, at 6 days post booster. In addition, vaccine hSBA seroresponse, seroprotection and GMTs to serogroups A, C, W and Y were determined following MenACYW-TT booster alone or co-administered with MenB-T or 4CMenB.