Immunogenicity and safety of a quadrivalent meningococcal tetanus toxoid-conjugate vaccine (MenACYW-TT) in adults 56 years of age and older: a Phase II randomized study

MenACYW-TT is an investigational quadrivalent meningococcal conjugate vaccine intended for the prevention of invasive meningococcal disease (IMD) caused by serogroups A, C, W, and Y in individuals aged 6 weeks and above. This Phase II, randomized, open-label, multicenter, exploratory study assessed the safety and immunogenicity of MenACYW-TT compared with a quadrivalent meningococcal polysaccharide vaccine (MPSV4) in 301 healthy adults aged ≥56 y in the US (NCT01732627). Participants were randomized 2:1 to receive MenACYW-TT or MPSV4. Serum bactericidal assays using human (hSBA) or baby rabbit (rSBA) complement were used to measure functional antibodies against meningococcal serogroups A, C, W, and Y at baseline and 30 d post-vaccination. Safety data were collected up to 30 d post-vaccination. Proportions of study participants with hSBA titers ≥1:8 against serogroups A, C, W, and Y were increased at Day 30 compared with baseline in both vaccine groups. The proportions of participants with hSBA titers ≥1:8 after MenACYW-TT vaccination were comparable to those after MPSV4 vaccination for serogroups A and C (A: 93.8% vs. 85.1%; C: 74.9% vs. 62.8%) and distinctly higher than after MPSV4 for serogroups W and Y (W: 79.5% vs. 60.6%; Y: 80.5% vs. 59.6%). Proportions of participants with rSBA titers ≥1:8 were comparable between vaccine groups for all four serogroups. The reactogenicity profiles of both vaccines were similar. Most unsolicited adverse events (AEs) were of Grade 1 or Grade 2 intensity, and no serious AEs were reported. The MenACYW-TT conjugate vaccine was well tolerated and immunogenic in adults aged ≥56 y.