Ability of the MenB-fHbp vaccine to provide immune protection against meningococcal serogroup B ST-1161 UK university “South West Outbreak” strain isolates

In 2021/22, the UK Health Security Agency reported an excess in cases of invasive meningococcal disease (IMD) caused by a meningococcal serogroup B (MenB) ST-1161 strain in South West (SW) England, primarily affecting university students. Here, we present a phylogenetic analysis of the "SW outbreak" strain, assess potential coverage provided by MenB vaccines using sequence-based tools and, for three representative outbreak isolates, evaluate the breadth of coverage provided by bivalent fHbp MenB vaccine (MenB-fHbp; Trumenba®)-containing vaccines and the susceptibility of isolates to antisera of vaccine recipients. The genomic analysis indicated that of the 16 SW outbreak strain isolates obtained, one isolate possessed an allele for fHbp peptide 1/B24 and 15 possessed the fHbp peptide 13/B09 allele. The Meningococcal Deduced Vaccine Antigen Reactivity (MenDeVAR) index and the Genetic Meningococcal Antigen Typing System (gMATS; two sequence-based classification tools) predicted that the fHbp antigen in the 4-component MenB vaccine (4CMenB; Bexsero®) covered the fHbp peptide 1/B24, but that coverage of the fHbp peptide 13/B09 was unpredictable. Meningococcal Antigen Surface Expression (MEASURE, a flow cytometry-based assay) data indicated a high probability of susceptibility to MenB-fHbp-induced antibodies. This was confirmed by immune response data (serum bactericidal antibody assay using human complement) that demonstrated cross-reactivity of antibodies induced by MenB-fHbp-containing vaccines to the fHbp peptide 13/B09 and 1/B24 in the outbreak strains. These analyses indicate that MenB-fHbp-containing vaccines were likely to have provided protection against the strains associated with the UK MenB IMD SW outbreak.