MenACWY-TT Vaccine Evaluated in Patients With Anatomic/Functional Asplenia

The quadrivalent meningococcal ACWY-tetanus toxoid conjugate vaccine (MenACWY-TT) was found to be safe and effective among high-risk children and adolescents aged 1–17 years. 

Having functional or anatomic asplenia places an individual at higher risk for meningococcal disease. For this study, a team of researchers conducted a Phase 3, open-label, controlled, non-randomized trial to compare the immunogenicity and safety of 1 and 2 doses of MenACWY-TT in children and adolescents with impaired splenic activity (high-risk group; n=40) vs age-matched healthy controls (control group; n=40). 

Immune responses were measured by serum bactericidal activity assays using rabbit (rSBA) and human (hSBA) complement and by the level of antibodies against polysaccharides of the 4 vaccine serogroups. Vaccine response rates (VRRs) were defined as 4-fold increases from pre-vaccination levels or titers ≥1:32 (rSBA)/≥1:8 (hSBA). In addition, adverse events 4 and 31 days post-vaccination were documented; serious adverse events and new onset of chronic illnesses (NOCIs) were documented throughout the study.

Results showed after the first MenACWY-TT dose, the rSBA VRRs were 92.5–100% and hSBA VRRs were 55.6–77.1% across the vaccine serogroups for both study arms. After the second MenACWY-TT dose, study patients demonstrated rSBA and hSBA VRRs of 73.0–100% across vaccine serogroups. 

Compared to baseline levels, the rSBA and hSBA geometric mean titers for each serogroup increased for both study arms (≥13.1-fold). Moreover, polysaccharide antibody concentrations ≥2.0µgmL were observed in ≥84.4% of patients. 

Four patients in the high-risk group and one patient in the control group reported serious adverse events but they were not vaccine-related; no NOCIs were identified. 

“Our study demonstrated for the first time that 1 or 2 MenACWY-TT doses induced functional (rSBA and hSBA) and anti-PS antibodies to the 4 serogroups in children and adolescents at high-risk for meningococcal disease,” the authors write. “These results support the use of MenACWY-TT in high-risk groups, especially asplenic children and adolescents.”

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