Session Title: VACCINE AND PREVENTION
ANTIBODY PERSISTENCE AND IMMUNE MEMORY 15 MONTHS AFTER MENINGOCOCCAL TETRAVALENT TETANUS-TOXOID CONJUGATE (ACWY-TT) VACCINE IN TODDLERS AND 3-5 YEAR-OLDS
M. Knuf1, A. Prieler2, J. Poolman3, P. Vink3, D. Boutriau3
1Johannes Gutenberg-Universität, Mainz, Germany, 2Private Practice, Neufeld/Leitha, Austria, 3GlaxoSmithKline Biologicals, Rixensart, Belgium
Background: The highest incidence of meningococcal disease is in young children. Existing polysaccharide vaccines against serogroups A, C, W, Y offer short-lived protection and do not induce immune memory. An investigational ACWY-TT conjugate vaccine was immunogenic and well tolerated in a first study in toddlers and children.
Methods: Blood samples in this follow-up, phase II, open randomized study (104704/NCT00126984) were collected 15 months after a single dose of ACWY-TT or control vaccine (monovalent MenC-CRM at 12-14 months, and ACWY-polysaccharide [MenACWY-PS] at 3-5 years of age). Subjects vaccinated toddlers received 1/5th dose of MenACWY-PS vaccine and were assessed one month after for boostability of the primary response. Serum bactericidal antibodies were assessed using rabbit complement source (rSBA, cut-off ≥1:8).
Results: The percentage of subjects with persisting rSBA titres ≥1:8 was significantly higher after ACWY-TT than control for all serogroups, except W-135 in the 3-5 year-olds (Table). One month after MenACWY-PS challenge in toddlers, GMTs (adjusted values) were significantly higher (for A: 3246.0vs.529.9, W-135: 9675.6vs.1439.2 and Y: 5840.6vs. 521.8) or not significantly different (for C: 6094.2vs. 5264.0) in ACWY-TT versus MenC-CRM primed subjects, indicating boostability by ACWY-TT priming.
Conclusion: The ACWY-TT vaccine induced persisting immune responses to all four serogroups in ≥ 92.3% of toddlers and 100% of 3-5 year-olds. Boostability after priming was successfully demonstrated.