New Zealand Epidemic Strain Meningococcal B Outer Membrane Vesicle Vaccine in Children Aged 16–24 Months


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Abstract

Background:New Zealand has experienced an epidemic of Neisseria meningitidis dominated by strain B:4:P1.7b,4 since 1991. Children younger than 5 years are at highest risk. Previous serogroup B outer membrane vesicle (OMV) strain specific vaccines have shown variable efficacy in this age group.Objective:To evaluate the immunogenicity, reactogenicity and safety in 16–24-month-old children of an OMV vaccine developed against the New Zealand epidemic strain.Methods:Children (332) aged 16–24 months were randomized to receive the New Zealand candidate vaccine made using strain NZ98/254 (B:4:P1.7b,4) or the Norwegian parent vaccine made using strain 44/76 (B:15:P1.7,16). Vaccines (25 μg/dose) were administered at 0, 6 and 12 weeks in this observer-blind trial. Immune response was measured by serum bactericidal assay and enzyme-linked immunosorbent assay. Sero-response was defined as a 4-fold or greater rise in serum bactericidal antibody titer compared with baseline, with titers <1:4 required to increase to ≥1:8 to be considered a sero-response. Local and systemic reactions were monitored for 7 days after vaccination.Results:Sero-response against NZ98/254 was achieved after 3 doses in 75% (95% CI: 69–80%) receiving the New Zealand candidate vaccine by both intention to treat (ITT) and per protocol (PP) analyses. In Norwegian parent vaccinees this was seen in 3% (0–12%) (ITT) and 4% (0–13%) (PP). Vaccines were well tolerated with no vaccine-related serious adverse events.Conclusion:The New Zealand candidate vaccine administered to these 16–24-month-old children in 3 doses was safe and elicited a promising immune response against the candidate vaccine strain NZ98/254 (N. meningitidis B:4:P1.7b,4) contributing to vaccine licensure for this age group.

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