METHODS: Children previously immunized, as part of a randomized controlled trial, with 2 doses of 4CMenB vaccine at 12–24 months of age received a booster at 4 years of age. Vaccine-naive age-matched toddlers received 2 doses of 4CMenB. Human serum bactericidal antibody titres against reference strains H44/76, 5/99, NZ98/254 and M10713 were evaluated before and after innoculation with 4CMenB vaccine in 4-year-old children.
RESULTS: Of 332 children in the study, 123 had previously received 4CMenB and 209 were vaccine-naive controls. Before the booster, the proportions of participants (previously vaccinated groups compared with controls) with hSBA titres of 1:5 or more were as follows: 9%–11% v. 1% (H44/76), 84%–100% v. 4% (5/99), 0%–18% v. 0% (NZ98/254) and 59%–60% v. 60% (M10713). After 1 dose of 4CMenB in previously immunized children, the proportions of participants achieving hSBA titres of 1:5 or more were 100% (H44/76 and 5/99), 70%–100% (NZ98/254) and 90%–100% (M10713).
INTERPRETATION: We found that waning of hSBA titres by 4 years of age occurred after 2 doses of 4CMenB vaccine administered at 12–24 months, and doses at 12–24 months have a priming effect on the immune system. A booster may be necessary to maintain hSBA titres of 1:5 or more among those children with increased disease risk. Trial registration: ClinicalTrials.gov, no. NCT01717638