SERO-REPLACEMENT WITH NON-VACCINE SEROTYPES POST INTRODUCTION OF PCV10 IN NASOPHARYNX OF CHILDREN IN A RURAL COMMUNITY IN PAKISTAN
Ten-valent pneumococcal vaccine (PCV10) was introduced in Pakistan’s immunization program in 2012. It is important to monitor changing sero- epidemiology post introduction for relevance of existing vaccine formulation.
From 2014 to 2018, children under the age of 2 years were enrolled from a rural district in Pakistan. Nasopharyngeal swabs were collected and serotyping was done using Multiplex PCR.
Of the 3140 children enrolled, pneumococcal isolates were detected in 2370(75%). VT carriage decreased from 16·1% to 9·6% (p-value< 0·001) over 4 years. There was a significant decline in VT serotypes 6B, 9V/9A and 19F only. The carriage of serotype 19A significantly increased from 4.0% to 6.8% (p-value< 0·001). This increase was more pronounced in vaccinated group. There was no significant change in the ten most common NVT serotypes except for 10A, which increased over time. There was no decline noted in carriage rate for serotype 6A.
We observed an ongoing shift in the pneumococcal carriage of serotypes in children in the rural community. Since the pneumococcal serotypes associated with carriage and Invasive disease are constantly changing, monitoring is necessary to assess the impact of the vaccine and to develop better vaccination strategies.