530 Persistence of Immune Response to Candidate Meningococcal Serogroups A, C, W-135, Y Tetanus Toxoid-Conjugated Vaccine (MenACWY-TT) up to 42 Months Following Primary Vaccination

Abstract

Background and aims: A primary dose of the candidate meningococcal A, C, W-135, Y tetanus toxoid-conjugated vaccine (MenACWY-TT) was immunogenic and well tolerated in subjects aged 15- 19 years (NCT00126945). Here, the persistence of the immune response to MenACWY-TT was compared with the MenA, C, W-135, Y polysaccharide vaccine Mencevax® ACWY (MenPS), and was evaluated up to 42 months after primary vaccination.Methods: This series of phase II, open, controlled persistence studies included subjects who received one dose of MenACWY-TT (N=24) or MenPS (N=26) in study NCT00126945. Persistence of functional antibodies, detected by serum bactericidal activity assay using rabbit serum as exogenous source of complement (rSBA, cut-off 1:8), was determined at 18, 30 and 42 months post-vaccination. Serious adverse events (SAEs) were recorded retrospectively up to 42 months post-vaccination.Results: rSBA titres ≥1:8 and geometric mean titres (GMTs) for the available timepoints are shown in the Table. All subjects in each group had rSBA titres ≥1:8 against all serogroups at all timepoints except for the MenPS group against MenC at Month 42. GMTs were higher than pre-vaccination levels at all timepoints post-vaccination in both groups. No SAEs related to vaccination were reported.Table Full size tableConclusions: All subjects receiving MenACWYTT retained rSBA titres ≥1:8 up to 42 months after primary vaccination, indicating that seroprotection following primary vaccination extends more than 3 years.Mencevax is a trademark of GlaxoSmithKline group of companies.