Do the protein-based meningococcal group B vaccines, 4CMenB and MenB-fHbp elicit serum bactericidal antibody against meningococcal serogroup X clonal complex 181?

BACKGROUND: Bexsero (4CMenB) and Trumenba (MenB-fHbp) were designed and licensed to protect against meningococcal serogroup B disease, however, the antigens in these vaccines are shared among other meningococcal serogroups. This study assessed the immunogenicity of the two licensed serogroup B vaccines against a hyperinvasive serogroup X strain. METHODS: Sera from adults immunised with either 4CMenB (before and after 1, 2 or 3 doses of vaccine) or MenB-fHbp (before and after 2 doses) were assayed in the Serum Bactericidal Antibody (SBA) assay against serogroup X BF 2/97. RESULTS: A four-fold increase in SBA titres were seen in 70.0% (95% CI: 45.7-88.1) and 51.5 % (95% CI: 41.3-61.6) of subjects following 2 doses of 4CMenB and MenB-fHbp, respectively. A significant increase in SBA GMT and percentage of subjects with SBA titres ≥4 from baseline to post two doses of both serogroup group B vaccines was observed. CONCLUSIONS: These data provide evidence that the licensed serogroup B vaccines can induce bactericidal antibodies against serogroup X, but it is noted the optimal control for serogroup X would be use of a conjugate vaccine that reduces acquisition of carriage as well as giving direct protection.