Meningococcal quadrivalent ACYW-TT conjugated vaccine at 6–23 months: phase III study (US/Puerto Rico)

Background A quadrivalent meningococcal tetanus toxoid-conjugate vaccine, MenACYW-TT, was developed to provide broad protection against invasive meningococcal disease across all age groups. We evaluated the immunogenicity and safety of MenACYW-TT as a two-dose series (1 + 1 schedule) co-administered with routine pediatric vaccines to infants from 6 months of age. Methods This phase III modified double-blind, randomized study (NCT03691610) enrolled healthy infants ( n = 750) and toddlers ( n = 200). Infants were randomized 1:1 to receive MenACYW-TT (Group 1) or another quadrivalent conjugate vaccine, MenACWY-CRM (Group 2) at ages 6–7 and 12–13 months, co-administered with routine vaccines. Toddlers were randomized 1:1 to receive MenACYW-TT (Group 3) or another quadrivalent conjugate vaccine, MenACWY-DT (Group 4) at ages 17–19 and 20–23 months. Functional antibodies against the four meningococcal serogroups were assessed by serum bactericidal antibody assay using human complement (hSBA). Safety was assessed up to 6 months post-vaccination. Results Seroresponse to MenACYW-TT was non-inferior to that with MenACWY-CRM against all four serogroups (seroresponse rates 30 days post-dose 2 were 89.4–99.3% and 82.9–97.7%, respectively). All vaccines were well tolerated. Conclusions These findings support MenACYW-TT administration as a two-dose series in children from 6 months of age. Study registration Clinicaltrials.gov: NCT03691610. Impact When administered as a two-dose series (1 + 1 schedule), MenACYW-TT demonstrated comparable/higher immunogenicity to MenACWY-CRM (ages 6–7 and 12–13 months) and the safety profiles of these quadrivalent meningococcal vaccines were similar. MenACYW-TT was non-inferior to MenACWY-CRM in terms of seroresponse rates and proportion of participants with antibody titer ≥1:8 after a second dose at age 12–13 months. This phase III study is the first to confirm the safety and immunogenicity of MenACYW-TT in infants and supports its use as a two-dose series from 6 months of age.