Durability of immunogenicity and strain coverage of MenBvac, a meningococcal vaccine based on outer membrane vesicles: Lessons of the Normandy campaign.

OBJECTIVES: MenBvac® is an outer membrane vesicle (OMV)-based meningococcal vaccine. From 2006 to 2012, it was used to control a clonal B outbreak in Normandy (France). We aimed to analyse the durability of the response against the epidemic strain and coverage beyond the vaccine strain. These data should help to optimize the use of OMV-containing vaccines, such as the new 4CMenB/Bexsero® recombinant vaccine.

METHODS: Serum bactericidal activity (SBA) was measured in two cohorts of children who received their first dose of MenBvac® at 1-5years of age and accepted to provide a blood sample either one or four years after a 2+1+1 schedule. All sera were tested against the outbreak strain. Sera from responder subjects were also tested against 12 additional B or C strains which were chosen to entirely, partially, or not at all match the two variable regions (VR1 and VR2) of the PorA vaccine strain.

RESULTS: Only 47.9% and 31.3% of subjects showed an SBA titre consistent with protection one and four years, respectively, after the last boost. Protective SBA titres were observed in all sera against B or C strains that entirely matched P1.7,16, and was high (75-100%) for all but one strain that partially matched VR1 or VR2. Extrapolating our data to the OMV component of 4CMenB/Bexsero® suggests that 14.5% of the current B strains would be covered based on PorA matching to the OMV component of 4CMenB/Bexsero® (regardless of the coverage of the three other vaccine components).

CONCLUSIONS: Our data confirm that OMV-based vaccines elicit short-lasting SBA titres and may require repeated booster injections. However, strain coverage may be greater than expected.