Population genomics of post-vaccine changes in pneumococcal epidemiology

Sequencing of the genomes of a large collection of Streptococcus pneumoniae, a respiratory pathogen that is a major cause of pneumonia, bacteraemia and meningitis, is reported in Nature Genetics. This provides insights into how the 2000 introduction of polysaccharide-protein conjugate vaccine (PCV7) for immunization of children in the USA influenced rates of disease and drug resistance.

Nicholas Croucher and colleagues sequenced the whole genomes of 616 asymptomatically carried pneumococci, obtained from children living in Massachusetts from health surveys during 2000-2007. They find that the pneumococcal population was disrupted by introduction of PCV7, largely related to replacement of vaccine types (VT) strains with non-VT relatives.They show that changes in pneumococcal serotype are a primary explanation for the decline in rate of invasive pneumococcal disease following the introduction of the vaccine.