2462. Immunogenicity and Safety of a Quadrivalent Meningococcal Conjugate Vaccine (MenACYW-TT) Administered in Individuals 56 Years of Age and Older

BACKGROUND: The MenACYW-TT conjugate vaccine is a quadrivalent meningococcal vaccine candidate intended for global use in all age groups. This Phase III study evaluated the safety and immunogenicity of the vaccine when compared with a licensed quadrivalent meningococcal polysaccharide vaccine (MPSV4) in adults ≥56 years of age. METHODS: A randomized, modified double-blind, multicenter study (NCT02842866) was conducted in 907 healthy adults in the United States. Participants were randomized to receive a single dose of either MenACYW-TT conjugate vaccine or MPSV4, stratified according to age into 2 subsets: 56 to 64 and ≥65 years. Descriptive analyses were also planned for age subsets 65–74 years and ≥75 years. Serum bactericidal assay with human (hSBA) and baby rabbit (rSBA) complement was used to measure antibodies against serogroups A, C, Y, and W test strains at baseline and 30 days after vaccination. Safety data were collected up to six months post-vaccination. RESULTS: Non-inferiority of immune responses was demonstrated between MenACYW-TT conjugate vaccine and MPSV4 based on percentages of subjects achieving hSBA vaccine seroresponse for serogroups A, C, Y, and W at Day 30 compared with baseline. The proportions of individuals with hSBA ≥ 1:8 obtained after MenACYW-TT conjugate vaccine were higher than those after MPSV4 for all four serogroups (A: 89.4% vs. 84.2%; C: 90.1% vs. 70.9%; W: 77.4% vs. 63.0%; Y: 91.7% vs. 67.7%). Overall, the results were similar in the three age substrata. Percentages of participants with post vaccination rSBA ≥ 1:128 were numerically higher for all serogroups in subjects vaccinated with MenACYW-TT conjugate vaccine. A difference in the local reactogenicity profiles was observed between the two vaccine groups, possibly influenced by the different routes of administration. Most unsolicited adverse events were of Grade 1 or Grade 2 intensity. No vaccine related serious adverse events were reported. CONCLUSION: MenACYW conjugate vaccine was immunogenic and well tolerated when administered to individuals ≥56 years of age. Such a vaccine will offer an alternative for the prevention of invasive meningococcal disease in areas of the world where only polysaccharide vaccines are currently available for immunization of older adults. DISCLOSURES: A. Esteves-Jaramillo, Sanofi Pasteur: Employee, Educational support and Salary. D. Neveu, Sanofi Pasteur: Employee, Salary. M. S. Dhingra, Sanofi Pasteur: Employee, Educational support and Salary.