Pneumococcal pneumonia is a major global disease. Safe and effective vaccines have been available for over two decades, but vaccine introduction in many low-middle income countries is frustratingly slow. This inequity strikes hard at children in Asia, where more than 40% of pneumonia deaths occur, and where extreme antibiotic use leads to widespread antimicrobial resistance (AMR).
Currently licensed pneumococcal conjugate vaccines (PCVs) cover a small subset of the most common serotypes. Vaccine introduction leads to profound reductions in pneumococci targeted by PCVs. These vaccine-type pneumococci tend to carry AMR determinants, so that PCV introduction has reduced AMR in some settings. Evidence that vaccine introduction reduced AMR in Asia would be powerful, but this is largely unknown.
Over time, PCV introduction leads to the emergence of non-vaccine types. These replacers can include virulent strains and new serotypes which can evade vaccine-induced protection. Alongside these changes, some vaccine-types remain stubbornly persistent. Very little is understood about such processes, particularly for Asia.
Here I will present data from a large pneumonia surveillance study in Mongolia to measure the impact of PCV introduction on nasopharyngeal carriage. We have applied sensitive methods to detect and characterise the pneumococci and used genomics and experimental models to identify important changes to the pneumococcal population. Together these data provide important evidence to support vaccine introduction and maintenance in Asia and beyond.