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

OBJECTIVES: 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 immunized with either 4CMenB (before and after one, two, or three doses of vaccine) or MenB-fHbp (before and after two doses) were assayed in the serum bactericidal antibody (SBA) assay against serogroup X strain BF 2/97. RESULTS: A four-fold increase in SBA titers was observed in 70.0% (95% confidence interval: 45.7-88.1) and 51.5% (95% confidence interval: 41.3-61.6) of subjects after 2 doses of 4CMenB and MenB-fHbp, respectively. A significant increase in SBA geometric mean titers and percentage of subjects with SBA titers greater than or equal to four from baseline to after two doses of both serogroup group B vaccines was observed. CONCLUSION: 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 and gives direct protection.