Serotype and clonal distribution dynamics of invasive pneumococcal strains after PCV13 introduction (2011-2016): Surveillance data from 23 sites in Catalonia, Spain.

BACKGROUND:The objective of this study is to describe incidence and shifts of serotype and clonal distribution of invasive Streptococcus pneumoniae strains in four different age groups (65 years) during a period of intermediate PCV13 vaccination coverage (2011-2016) in Catalonia, Spain. METHODS:We included all pneumococcal strains systematically sent to the Catalan support laboratory for molecular surveillance of invasive pneumococcal disease (IPD) located at Hospital Sant Joan de Deu, Barcelona. Two study periods were considered: 2011-13, early PCV13 vaccination period (EVP) and 2014-2016, late vaccination period (LVP). RESULTS:A total of 2142 strains were included in the study. Five years after intermediate introduction of PCV13 in our population, a significant decrease of overall incidence of IPD in children 65 years. Results found when comparing both periods were consistent with IRRs observed year by year. In children 65 years the most frequently isolated serotypes were 3, 19A and 7F vs 3, 14 and 12F, respectively. Regarding clonal complexes (CCs) expressing mainly PCV13 serotypes, significant decreases of the proportions of CC306, CC191 and CC320 were observed, while CC156 showed a significant increase. As for CCs expressing mostly non-PCV13 serotypes, significant increases in ST989, CC53 and CC404 were showed. CONCLUSIONS:Despite low vaccine coverage in our setting a significant decrease of incidence of IPD was observed in children younger than 5 years. The modest indirect protection against vaccine serotypes causing IPD in elderly indicate the need for the inclusion of more serotypes in future high-valent PCV and vaccinating old adults should be considered