A phase IIIb study (MET59) has revealed the long-term immune response and effectiveness of a booster dose of MenACYW-TT (MenQuadfi®) in adolescents and young adults previously primed with either MenACYW-TT or MCV4-CRM (Menveo) conjugate vaccines. The study, conducted across 29 centers in the USA and one in Puerto Rico, aimed to assess the persistence of meningococcal antibodies 3–6 years after the initial vaccination and the subsequent immune response following a MenACYW-TT booster. This research is particularly relevant given the vulnerability of adolescents to meningococcal disease and the importance of sustained protection through booster doses.
The study enrolled 570 participants aged 13 to 24 years, all of whom had received a single dose of either MenACYW-TT or MCV4-CRM 3–6 years prior in earlier studies. A complementary analysis focused on a subset of adolescents (n=470) who received their priming dose between 10 and 12 years, aligning with the Advisory Committee on Immunization Practices (ACIP) recommendations. This analysis specifically evaluated the persistence of the immune response following the primary vaccination with either MenACYW-TT (n=340) or MCV4-CRM (n=130).
Immune Persistence and Booster Response
Immune persistence was evaluated using serum bactericidal antibody assays with human complement (hSBA). The analysis revealed that while seroprotection rates (hSBA titers ≥1:8) remained high 30 days post-priming, they declined over 3–6 years. For MenACYW-TT, seroprotection rates decreased to 71.1% for serogroup A, 86.8% for serogroup C, 88.2% for serogroup W, and 82.3% for serogroup Y. Similarly, MCV4-CRM showed declines to 73.1% for serogroup A, 48.5% for serogroup C, 75.4% for serogroup Y, and 51.5% for serogroup W. Despite these declines, geometric mean titers (GMTs) remained higher than pre-priming levels, indicating long-term immune response persistence.
Following the MenACYW-TT booster, nearly all participants in both the MenACYW-TT- and MCV4-CRM-primed groups achieved seroprotective titers for each serogroup. The booster induced an anamnestic response, with GMT increases significantly higher than those observed after the priming vaccination across all serogroups.
Comparative Analysis of MenACYW-TT and MCV4-CRM
The study indicated that priming with MenACYW-TT consistently resulted in higher levels of hSBA antibody persistence for serogroups C, W, and Y compared to MCV4-CRM. Seroprotection rates and GMTs were notably higher in the MenACYW-TT group for these serogroups. However, persistence was similar in both groups for serogroup A.
Clinical Implications
The findings support the ACIP-recommended schedule of administering a meningococcal ACWY conjugate vaccine priming dose at 11–12 years, followed by a booster at 16 years. The data suggest that a single dose of MenACYW-TT induces an antibody immune response that persists for at least 3–6 years, providing continued protection against invasive meningococcal disease until the recommended booster age. "The results of our analysis support the ACIP-recommended schedule for routine administration of a priming dose of meningococcal ACWY conjugate vaccine at 11–12 years of age followed by a booster dose at 16 years of age."
