Neisseria meningitidis is the causative agent of meningococcal disease which has a mortality rate of 6%. Multi-locus sequence typing (MLST) of seven housekeeping genes classifies meningococci into genetic lineages termed clonal complexes (cc). A new vaccine, BEXSERO^®, incorporates four main meningococcal surface antigens: factor H binding protein (fHbp), Neisserial Heparin Binding Antigen (NHBA), Neisserial adhesin A (NadA) and porin A (PorA). The vaccine is most effective against isolates expressing antigenic variants fHbp-1, PorA serosubtype 1.4, and NadA-1,2/3. Based upon antigenic variation and different expression levels of these proteins by isolates, most studies predict a vaccine coverage of 66-88% of disease causing isolates within each jurisdiction.

The aim of this study was to analyse the sequence variability of meningococcal antigens and predict the coverage by the BEXSERO^® vaccine in Western Australia over the past 15 years.

The genomic DNA of 278 meningococcal strains isolated from patients was sequenced using Illumina paired ends. The short read sequence typing program (SRST2) was used to determine the allele of each MLST and antigen locus.

The majority of isolates (43%) belonged to cc41/44. Since 2010, cc41/44 has declined in prevalence as has the overall rates of disease. In the entire collection, 51%, 30% and 15% respectively possessed variants of fHbp-1, NadA-1,2/3 and PorA serosubtype 1.4. All strains encoded a gene for NHBA. Thus, 64% of isolates possessed 2 or more of the vaccine antigens. FHbp-1 prevalence predominated all other types pre-2005, but underwent temporal shifts post-2005. In 2008 and 2012, fHbp-3 predominated whilst the prevalence of fHbp-2 remained steady across the sample period.

In conclusion, the predicted coverage of strains by BEXSERO^® in Western Australia is similar to other reports worldwide. However, this study is the first to observe temporal shifts of fHbp over a 15 year time scale.