2456. Immunogenicity and Safety of a MenACWY-CRM Booster Dose 4-6 Years after Primary Quadrivalent Meningococcal Conjugate Vaccination in Healthy U.S. Adolescents and Adults
Session: Poster Abstract Session: Adolescent Vaccines
Saturday, October 6, 2018
Room: S Poster Hall
Background: Neisseria meningitidis serogroups A, B, C, W and Y are a leading cause of bacterial meningitis and sepsis worldwide. Infants <1 year, adolescents and young adults are at the highest risk. The U.S. Advisory Committee on Immunization Practices (ACIP) recommends routine MenACWY conjugate vaccination for adolescents at 11-12 years of age, with a booster dose 5 years later. We examined responses to a booster dose of MenACWY-CRM given 4-6 years after primary vaccination with a licensed quadrivalent meningococcal conjugate vaccine (NCT02986854).

Methods: 602 adolescents and adults aged 15-55 years who had received either MenACWY-CRM (N=301) or MenACWY-D (N=301) 4-6 years earlier, and a control group of vaccine-naïve participants (N=102) were enrolled at 37 centers across the U.S. and 701 overall received a single dose of MenACWY-CRM at Day 1, across study groups. Immunogenicity was evaluated pre-vaccination, either 4 or 6 days post-vaccination (sampling subgroups) and 29 days post-vaccination by serum bactericidal activity assay using human complement (hSBA). After vaccination, all participants were to be monitored for 7 days for reactogenicity, 29 days for unsolicited adverse events (AEs), and 6 months for occurrence of medically-attended events, AEs leading to withdrawal and serious AEs.

Results: Sufficiency of the immune response to a booster dose of MenACWY-CRM was demonstrated as the lower limit of the 1-sided 97.5% confidence interval for percentages of participants with hSBA seroresponse for each serogroup at 29 days post-vaccination was >75%, both in participants primed with MenACWY-CRM and MenACWY-D. Independent of quadrivalent meningococcal vaccine priming, >93% of participants achieved a seroresponse at day 29 post-booster. By day 6 post-booster, >47% of primed participants achieved hSBA titers ≥1:8 for MenA, >87% for MenC, >93% for MenW and >85% for MenY, and by day 29 almost all primed participants had seroprotective titers across all serogroups. Overall, the vaccine was well tolerated across participants in all 3 groups and no safety concerns were raised.

Conclusion: MenACWY-CRM induced robust boosting in adolescents and adults primed with a quadrivalent meningococcal conjugate vaccine 4-6 years earlier, with an acceptable clinical safety profile.

Funding: GSK Biologicals SA

Mary Tipton, MD1, Wendy Daly, MD2, Shelly Senders, MD3, Stanley L. Block, MD4, Pavitra Keshavan, MBSS, PhD5, Thembile Mzolo, PhD5 and Michele Pellegrini, MD, PhD6, (1)CopperView Medical Center, South Jordan, UT, (2)Brownsboro Park Pediatrics, Louisville, KY, (3)Senders Pediatrics, South Euclid, OH, (4)Kentucky Pediatric and Adult Research, Bardstown, KY, (5)GSK, Amsterdam, Netherlands, (6)GSK, Siena, Italy

Disclosures:

M. Tipton, None

W. Daly, None

S. Senders, None

S. L. Block, GSK: Research Contractor , Research support .

P. Keshavan, GSK Vaccines: Employee , Salary .

T. Mzolo, GSK Vaccines: Employee , Salary .

M. Pellegrini, GSK Vaccines S.r.l.: Employee and Shareholder , Salary .

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