Community carriage of pneumococcal serotypes in children was assessed pre- and post-PCV10 introduction in Nepal to monitor pneumococcal vaccine impact. Molecular serotyping by microarray enabled detection of multiple-serotype carriage plus non-encapsulated pneumococcal lineages, related Streptococcus species and selected antimicrobial resistance genes.
Nasopharyngeal swabs were collected from healthy Nepalese children in 2014-15 (pre-PCV10) and 2017-18 (post-PCV10). DNA was extracted from plate sweeps of 1,241 and 1,445 swab cultures for pre- and post-vaccine periods respectively and analysed by Senti-SP molecular serotyping microarray.
Comparing carriage among children pre- and post-PCV10, there was a decrease in PCV10 serotype carriage (37% vs 17%) and an increase in non-vaccine serotype carriage (67% vs 73%). There was no change for non-encapsulated pneumococcal lineages (16% vs 16%), an increase in related Streptococcal species (22% vs 25%) and an increase in detection of antimicrobial resistance genes (65% vs 74%). Multiple pneumococcal serotype carriage decreased (24% vs 16%) and multiple carriage including non-encapsulated pneumococci and related Streptococcal species also decreased (45% vs 41%).
Introduction of PCV10 in Nepal has resulted in a decrease in vaccine type carriage within two years. However, increases in carriage of non-vaccine types as well as antimicrobial resistance genes and related Streptococcal species were observed.