Background
Currently there are no licensed Group B streptococcus (GBS) vaccines, but a hexavalent-polysaccharide (Ia, Ib, II, III, IV, V), and a multivalent-adjuvanted-protein vaccines are in the pipeline. We set out to investigate the distribution of serotypes and vaccine-targeted proteins in disease-causing GBS in the UK.
Methods
GBS isolates were submitted for typing to the Streptococcus Reference Laboratory at the UK Health Security Agency between 2009-2023. A total of 1088 GBS genomes were characterised based on serotype, multi-locus sequence type and presence of alp1, alp2/3, rib and alphaC and antimicrobial resistance (AMR) genes.
Results
The genes encoding capsular serotypes in the hexavalent GBS vaccine were found in 98.6% (627/636) GBS in <1-year olds (98.2% of EOD, 100% of LOD cases) and 93.6% (378/404) adults (>18 years). Of 1088 sequences assessed against the four protein genes, 97.7% (1063) had one of the 4 proteins present (99.3% for EOD, 100% for LOD and 98.5% for adult), however differences were observed in the gene prevalence <1-year olds vs. adults: rib 60.1% vs. 29.2%, alp2/3 5.5% vs. 13.9%, alp1 18.1% vs. 27.5% and alphaC 15.3% vs. 28.0%. Additionally, 92.5% (1006/1088) of GBS had at least one AMR gene present, with 27.2% of genomes carrying macrolide resistance genes.
Conclusion
Though the presence of vaccine targeted proteins/serotypes differed between age groups, overall, nearly all analysed GBS would be covered by the hexavalent-polysaccharide GBS vaccine and protein-based GBS vaccine. These data provide evidence for the potential impact of inclusion of GBS into the vaccination programme.