The WHO has recommended the introduction of the PCV vaccine into childhood vaccination programs since 2007 in order to combat Streptococcus pneumoniae, one of the main agents responsible for lower respiratory tract infections in children under five. As the benefits of this strategy vary depending on the context, the vaccination coverage rate and the diversity of strains in circulation, the Mérieux Foundation carried out the PCV study to guide public health decision-making and strengthen the fight against pneumococcal infection in high-risk regions.
The study aimed to evaluate the prevalence of colonization by Streptococcus pneumoniae in a context where PCV had recently been deployed: it was conducted in hospital settings in Cambodia, India, and Paraguay in children under five and the adults they live with. Finalized in 2025, it made it possible to establish a central protocol for generating prevalence data across different epidemiological contexts.
The results issued by the GABRIEL network member laboratories in the three countries involved in the study show that pneumococcal colonization remains frequent among children despite the introduction of the vaccine: over 30% in India and Cambodia and nearly 40% in Paraguay. The study also highlighted the phenomenon of serotype replacement: the gradual replacement of vaccine serotypes by strains not included in the vaccine, indicating that serotypes continue to evolve.
This data confirms the importance of surveillance to ensure that vaccine policies can be adjusted and the emergence of new potentially pathogenic serotypes can be anticipated. In Paraguay, the study also showed that antibiotic resistance is frequent and growing relative to previous studies.
