YSPH EMD Seminar: “How serotype replacement threatens the success of pneumococcal vaccination programs worldwide”

Streptococcus pneumoniae is the leading cause of pneumonia mortality worldwide and is responsible for >300,000 deaths in children under 5 years of age each year. Childhood vaccination programs resulted in a decrease in disease caused by vaccine serotypes, but serotype replacement resulted in a simultaneous increase in carriage and disease caused by non-vaccine serotypes. A key driver of serotype replacement is capsule-switching, which is the expansion of non-vaccine serotypes within vaccine-type genetic lineages. Genetic analyses suggest that specific serotype pairs switch preferentially, but the mechanisms behind this remain poorly understood. Our work focuses on characterizing the fitness of capsule-switch variants and providing an improved understanding of genetic and metabolic constraints on this process. We aim to be ablet to predict capsule-switch variants that are most likely to emerge in the future and use this to guide serotype inclusion for next generation vaccines