Pneumococcal population in the era of vaccination: changes in composition and the relation to clinical outcomes

Background: Vaccination of infants with pneumococcal conjugate vaccines (PCV) has resulted in major shifts in circulating serotypes. Aim: To investigate the impact of PCV7 on the clonal composition of the pneumococcal population, and the relation of clonal lineages and clinical outcome. Materials & methods: By using multiple-locus variable number of tandem repeat analysis, we assessed the pneumococcal populations before (n = 1154), 2-3 years after (n = 1190) and 4-6 years after (n = 1244) the introduction of PCV7 in The Netherlands. Results: We found statistically significant shifts in clonal lineages within serotypes 1 and 12F based on multiple-locus variable number of tandem repeat analysis results after the implementation of PCV7. Within serotype 12F, the increasing clonal lineage was significantly more associated with pneumonia. Conclusion: Shifts in clonal lineages within serotypes could impact the outcomes of pneumococcal disease and fill the niche of the vaccine serotypes