title: Antibody persistence following MeNZB vaccination of adults and children and response to a fourth dose in toddlers.
abstract: BACKGROUND
  A New Zealand serogroup B meningococcal epidemic prompted trials of a strain-specific (B:4:P1.7-2,4) outer membrane vesicle vaccine (MeNZB).
  
  
  METHODS
  Adults, school children, and infants provided serum after three MeNZB doses to evaluate antibody persistence via serum bactericidal assay. Toddler (16-24 months) non-responders and responders received a fourth MeNZB dose 11 and 17 months after dose three respectively. Response was a ≥4-fold rise in bactericidal titre to a titre of ≥8.
  
  
  RESULTS
  Geometric mean bactericidal titres (GMTs), with 95% CI, after dose 3: adults: 27 (14-52), 5 (3-11), and 7 (3-15) at 1, 10, and 22 months; school children: 18 (13-25) and 4 (3-6) at 1 and 4 months; infants: 27 (19-39) and 2 (2-3) at 1 and 7 months. The titre achieved after priming significantly influenced persistence. Toddler non-responder GMTs were 4 (3-5) and 1 (1-1) at 1 and 11 months after dose 3 and 69 (46-106) 1 month after dose 4. Responder GMTs were 24 (19-30) and 3 (2-4) at 1 and 17 months after dose 3 and 259 (184-363) 1 month after dose 4. Dose 4 had no safety concerns.
  
  
  CONCLUSIONS
  Immune response to MeNZB was most sustained in adults. In infants, bactericidal titres decayed almost to baseline by 7 months after dose 3. Toddlers showed marked immune response following a fourth dose suggesting memory. Persisting antibody is likely to be necessary for ongoing protection, as seen with serogroup C meningococci.
authors: Epidemiology and Biostatistics, Community Paediatrics, School of Population Health—Tamaki Campus, University of Auckland, Auckland, New Zealand.
authors: Catherine
authors: C
authors: Jackson
authors: Diana
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authors: Lennon
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authors: Stewart
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