Bactericidal antibody persistence two years following immunization with two investigational serogroup B meningococcal vaccines at 6, 8 and 12 months and immunogenicity of pre-school booster doses: A follow-on study to a randomized clinical trial

BACKGROUND: In a previous study 60 infants receiving an nvestigational a serogroup B meningococcal vaccine containing recombinant meningococcal proteins alone (rMenB) or combined with an outer-membrane vesicle from Neisseria meningitidis (4CMenB) at 6, 8 and 12 months of age produced serum bactericidal antibodies (SBA) against meningococcal strains expressing vaccine antigens. We studied persistence of this response and the response to a booster dose of vaccine. METHODS: In this extension study, SBA titers were evaluated before and after a booster dose of rMenB or 4CMenB at 40 months of age. MenB vaccine naïve age-matched children served as a control group. RESULTS: Prior to the booster doses, the proportions of 4CMenB recipients with SBA titers ≥ 1:4 were 36% (n=14, 95% C.I. 13 - 65%) for strain 44/76-SL, 100% (77-100%) for 5/99, 14% (2-43%) for NZ98/254 and 79% (49 - 95%) for M10713. These percentages were 14 to 29% for rMenB recipients (n=14), except for 5/99 (93%, 66 - 100%). For controls (n= 40) these proportions were ≤ 3% for all strains except M10713 (53%, 36 - 68%).One month after the boosters, ≥ 93% of 4CMenB recipients had SBA titers ≥ 1:4 for all 4 strains. For controls receiving their first dose of 4CMenB, 23% (11% - 39%) had SBA titers ≥ 1:4 for NZ98/254, compared with 62% to 87% for the remaining strains. CONCLUSION: Bactericidal antibodies wane following infant immunization with rMenB or 4CMenB, but there is an anamnestic response to a booster dose. Booster doses of 4CMenB may be required to maintain immune protection through childhood and adolescence. CLINICAL TRIALS REGISTRATION NUMBER: NCT01026974.