Long-term effect of 10-valent pneumococcal conjugate vaccine on nasopharyngeal carriage of Streptococcus pneumoniae in children in Brazil.

UNLABELLED: Brazil introduced the 10-valent pneumococcal vaccine (PCV10) to the routine national immunization program (NIP) in March 2010. In 2017, we investigated the effects of PCV10 on nasopharyngeal carriage of vaccine-types (VT) and non-vaccine-types (NVT) of Streptococcus pneumoniae (Spn) among children living in São Paulo city. We also compared the prevalence of VT and NVT with previous carriage surveys performed in 2010 (baseline) and 2013.

METHOD: The carriage survey was conducted among 531 children, aged 12 months to <24 months, recruited from public Primary Health Units during the immunization campaign, using previous surveys methodology, except for qPCR, which was performed in the 2017 survey only.

RESULTS

No statistical difference was found in the prevalence of Spn either by culture (59.7%) or by qPCR (61.2%). Spn carriage increased from 40.3% (baseline) to 59.7% (2017 survey) (p < 0.001). Colonization by VT isolates significantly decreased by 90.9% (19.8-1.8%) and 95.5% (19.8-0.9%) in the 2013 and 2017 surveys, respectively, compared to that at baseline. NVT isolates increased significantly by 128% (19.6-44.8%) and 185% (19.6-55.9%) in the respective post-PCV10 surveys, most led to high prevalence of serotypes 6C (27%), 15B (9.8%), 19A (9.2%), 15A (6.0%), and 16F (5.7%). In 2017, reduction in serotype 6A (4.2-0.6%, p < 0.001) and increase in serotype 19A (1.8-6.0%, p = 0.001) were found; serotype 3 isolate was not detected in the present survey. We identified the emergence of 19A isolates CC320, associated with high penicillin (MIC ≥ 2.0 mg/L) and cefotaxime (MIC ≥ 1.0 mg/L) values.

CONCLUSION

After 7 years of PCV10 introduction in the NIP, colonization by VT among toddlers decreased substantially to a residual level, along with substantial serotype replacement by novel serotypes not present in any current conjugated pneumococcal vaccine and serotype 19A. The present findings can assist policy decisions in Brazil.