• Roger Baxter, Yaela Baine, Devayani Kolhe, Carmen I Baccarini, Jacqueline M Miller, and Marie Van der Wielen.
• From the *Kaiser Permanente Vaccine Study Center, Oakland, California; †Vaccines Discovery & Development, GSK Vaccines, King of Prussia, Pennsylvania; †Pharma Europe & EMAP, GSK Pharmaceuticals India Ltd, Bangalore, India; and §Clinical R&D, GSK Vaccines, Wavre, Belgium.
• Pediatr. Infect. Dis. J. 2015 Nov 1; 34 (11): 1236-43.

BackgroundWe evaluated antibody persistence after 1 dose of meningococcal serogroups ACWY tetanus toxoid (MenACWY-TT) or diphtheria toxoid (MenACWY-DT) conjugate vaccines and subsequent booster responses to MenACWY-TT.MethodsIn the initial phase II, open, multicenter study (NCT00454909), 872 participants aged 10-25 years received 1 MenACWY-TT or MenACWY-DT dose. In this study (NCT00715910), antibody persistence was evaluated at years 1, 3 and 5 by serum bactericidal activity assays using human complement (hSBA). At year 5, all participants received a MenACWY-TT booster dose. Immune responses at 1-month postbooster were compared with a control group including 101 participants aged 15-30 years who received a primary MenACWY-TT dose. Solicited and unsolicited adverse events were recorded for 4 and 31 days, respectively, followed by a 6-month extended safety follow-up.ResultsAt year 5, ≥79.5% of MenACWY-TT-primed (n = 170) and MenACWY-DT-primed (n = 45) participants had hSBA titers ≥1:8 for MenC, MenW and MenY, and ≥37.5% for MenA. For all serogroups, ≥85.7% and ≥67.1% of MenACWY-TT booster and primary dose recipients exhibited vaccine responses 1-month postmvaccination, respectively. Geometric mean titers were potentially higher in primed versus naive participants, with no potential difference between MenACWY-TT-primed and MenACWY-DT-primed participants (exploratory analyses). MenACWY-TT had a clinically acceptable safety profile.ConclusionsBefore the booster dose administration at year 5, hSBA-MenC, -MenW and -MenY antibody persistence was observed in most participants. However, only ≥37.5% of MenACWY-TT and 44.4% of MenACWY-DT recipients retained hSBA-MenA titers ≥1:8. MenACWY-TT booster doses elicited robust anamnestic responses, irrespective of the priming vaccine, and were well tolerated.

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