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.
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Funding This study was funded by the New Zealand Ministry of Health and Novartis Vaccines.
Competing interests DL: funding for travel received from Novartis Vaccines; PO and EY: employed by Novartis Vaccines during the study; DM: serum antibody assays were indirectly funded through a joint contract with the New Zealand Ministry of Health and Novartis Vaccines.
Ethics approval This study was conducted with the approval of the Auckland Regional Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.