• Corwin A Robertson, David P Greenberg, James Hedrick, Michael Pichichero, Michael D Decker, and Martha Saunders.
• Scientific and Medical Affairs Department, Sanofi Pasteur Inc., Discovery Drive, Swiftwater, PA 18370, USA. Electronic address: corey.robertson@sanofipasteur.com.
• Vaccine. 2016 Oct 17; 34 (44): 5273-5278.

BackgroundQuadrivalent meningococcal conjugate vaccines (MenACWY) were developed to offer long-term protection against invasive disease caused by serogroups A, C, W, and Y. Reduced MenACWY effectiveness within 5 years after primary vaccination (likely due to declining bactericidal antibody titers) has been described, particularly with respect to C and Y disease in the United States. We evaluated the safety and immunogenicity of a single booster dose of quadrivalent meningococcal polysaccharide diphtheria toxoid conjugate vaccine (MenACWY-D) in adolescents and adults who received a previous dose 4-6 years earlier.MethodsThis phase 2, open-label, multicenter study of 834 persons was conducted in the United States. Participants received a single 0.5-mL booster dose of MenACWY-D. Serogroup-specific bactericidal antibody geometric mean titers (GMTs) were measured with a serum bactericidal antibody assay using human complement (hSBA). Proportions of participants achieving antibody titers of ⩾1:8 for each vaccine serogroup on Days 6 and 28 were determined. Rates of adverse events (AEs), including serious adverse events (SAEs), were also assessed.ResultsBefore booster vaccination, 38.7-68.5% of participants had an hSBA titer ⩾1:8, depending on vaccine serogroup. By Day 6 post-vaccination, 98.2-99.1% of participants had hSBA titers ⩾1:8. By Day 28, >99% of participants achieved this threshold and the primary hypothesis (lower limit of the one-sided 95% confidence limit ⩾85% for each serogroup) was met. The GMT ratios (post-vaccination divided by pre-vaccination) at Day 28 ranged from 47.2 (serogroup A) to 209.1 (serogroup Y). Rates of AEs, including SAEs, were similar to those observed among adolescents and adults who received a primary dose of MenACWY-D in previous studies. There were no study discontinuations due to an AE and no deaths.ConclusionsBooster vaccination with MenACWY-D was safe and induced robust bactericidal antibody responses, consistent with immune memory, among adolescents and adults 4-6 years after primary vaccination. ClinicalTrials.gov registration: NCT01442675.Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

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