Background

The ten-valent pneumococcal conjugate vaccine (PCV10) was introduced in Nepal in 2015. We compared the nasopharyngeal carriage of PCV10 and non-PCV10 serotypes of pneumococcus between pre-vaccine (2015) and post-vaccine (2017-2018) years in two different regions of Nepal.

Methods

Nasopharyngeal samples obtained in healthy Nepalese children aged 6-59 months in urban (Patan, Kathmandu) and 6-23 months in rural (Okhaldhunga) settings were transported in STGG (Skim Milk-Tryptone-Glucose-Glycerol) media, cultured for pneumococcus and serotyped by the Quellung method.

Results

The carriage prevalence decreased for all PCV10-type serotypes except 7F in both the settings. PCV10-type prevalence decreased from 29.7% in rural and 17.2% in urban children pre-vaccine to 9.0% and 8.6% post-vaccine, respectively. Pre-vaccine, the most frequently found serotypes in both settings were 19F, 6B, 14. Post-vaccine, the non-PCV10 serotypes were more common; serotypes 34, 6C, 19A and 15B were most common in rural and 6A, 34, 11A, 6C and 15B in urban settings.

Conclusions

Since the introduction of PCV10, carriage prevalence of PCV10 serotypes have reduced and non-PCV10 serotypes have increased in both settings raising the possibility of replacement disease. Continued monitoring of changes in PCV10-serotypes and non-PCV10 serotypes, especially those covered by PCV13, is important to assess vaccine impact.

Background

S. pneumoniae is a major cause of bacterial pneumonia and an important cause of invasive bacterial disease (IBD) in children under-five years of age in Nepal. Pneumococcal conjugate vaccine, PCV10, was introduced in 2015 with a 2+1 schedule.

Methods

We assessed the programmatic impact of PCV10 introduction using surveillance for nasopharyngeal (NP) colonisation, pneumonia and IBD. NP swabs from pneumonia inpatients and from healthy children, blood cultures from inpatients with suspected IBD, and chest x-rays from inpatient pneumonia cases were obtained over a 6-year period (2014-2019).

Results

The proportion of pneumonia cases with radiographic endpoint-consolidation (likely bacterial) was 34% lower (95%CI 19-46%) in 2018 compared with the pre-vaccine period (2014-2015). Vaccine serotype (VT) carriage in children under 2-years of age with pneumonia in 2019 was 78% lower (95%CI 30-93%) than in the pre-vaccine period.

Among healthy 6-23 month old children (urban and rural cohorts), VT-carriage declined 74% (95%CI 43-82%) by 2019. An increase in PCV13-additional-serotype carriage was seen in 2018 among rural-children (prevalence-ratio 1.65, 95%CI 1.17-2.32), but not urban-children.

Serotype 1 remains the dominant serotype detected in cases of invasive pneumococcal disease.

Conclusions

A decrease in prevalence of endpoint-consolidation-pneumonia and a decrease in vaccine-serotype circulation have been observed post PCV introduction in Nepal.