Neisseria meningitidis is a major cause of invasive meningococcal disease (IMD) that affects mostly infants and children, with a fatality rate of around 10%. In the United States (US), serogroup B (NmB) strains cause approximately 30% of all IMD cases and >60% of cases in infants aged <1 year. The most effective way to prevent IMD is vaccination. The 4-component MenB-4C (Bexsero) vaccine includes factor H binding protein (fHBP), neisserial heparin binding protein (NHBA), neisserial adhesin A (NadA), and PorA-containing outer membrane vesicles. Currently, the human serum bactericidal assay is the accepted method for assessing NmB vaccine efficacy but requires large volumes of serum and complement.
The meningococcal antigen typing system (MATS) addresses these limitations; it tests isolated NmB strains by combining a sandwich enzyme-linked immunosorbent assay (ELISA) to measure the levels of expression and immune reactivity of the three recombinant MenB-4C antigens, fHBP, NHBA, and NadA, with genotyping of PorA variable 2 region (VR2). Coverage is predicted for any strain when antigen relative potency (RP), the content of the three vaccine antigens relative to reference strains, exceeds antigen-specific positive bactericidal thresholds (PBT), established in previous inter-laboratory studies, and/or when PorA VR2 subtype 4 is present. In this study, MATS was used to test 384 invasive NmB strains collected in the US from 2015-2018 to estimate predicted MenB-4C coverage. Of the 384 strains tested, coverage was estimated for 360 strains with results for all four vaccine antigens.
The coverage prediction of the strains is 74.2% with a 95% coverage interval of 54.4% - 87.5%. As MATS is designed to provide a conservative estimate of potential vaccine coverage, these values should be interpreted as a lower-bound prediction. The distribution of the strains covered shows that 46.4% are predicted to be covered by a single antigen while 27.8% are predicted to be covered by more than one antigen, indicating that the vaccine has the potential to offer protection against a majority of disease-causing strains. These results demonstrate the utility of MATS as a standardized tool for predicting MenB-4C vaccine antigen distribution among NmB strains, supporting public health surveillance, and informing prevention strategies.