Background

Serotype-1, a major cause of invasive pneumococcal diseases (IPD), is a part of PCV10 and PCV13 formulations. Multiple countries have reported a positive impact on serotype-1 after vaccine introduction. This study aims to observe the trend of serotype-1 in Bangladesh, their sequence types (ST), and GPSCs using whole-genome sequence (WGS), from 2004 to 2021, following the introduction of PCV10 in 2015.

Methods

Child Health Research Foundation has been conducting IPD surveillance since 1993 at four different hospitals in Bangladesh and identified 164 serotype-1 cases since. WGS was done for all culture-positive isolates (n=94) and analyzed to detect serotypes, GPSCs and STs; also reference mapped to generate a phylogenetic tree.

Results

Since 2004, we identified overall 9% (112/1,280) serotype-1 among all IPD cases. However, this ratio increased in the post-PCV period, from a yearly average of 10.2% to 10.8%. The affected age group has also changed, from 82% to 43% cases (pre- vs post) among <5y children (Figure 1).

Remarkably, the change was reflected in the phylogenetic tree, showing specific clusters for pre- and post-PCV cases (Figure 2), suggesting some changes in their genomic background, although the dominance of GPSC-2 (100%) and ST303 (94%) remains.

Conclusions

Our results suggest changes in the serotype-1 population of Bangladesh since the PCV10 introduction. Both the burden and age group have changed, along with some indicative genomic changes. Further, we will explore the evolutionary background (using BEAST), relate with clinical and epidemiological data, and the possible role of vaccines – to present at ISPPD, Toronto.