Mismatch Between Malaria Vaccines and Local Parasite Strains in Ethiopia

A recent study in Ethiopia reveals that local malaria parasite strains differ genetically from those targeted by current vaccines, potentially reducing their effectiveness.

Transcript

The recent introduction of two malaria vaccines in sub-Saharan Africa represents a major success in global health, and the culmination of decades of research and development. The two jabs – RTS,S and R21 – target a protein on the surface of the malaria parasite as it enters the skin, called the circumsporozoite protein, or CSP. The vaccines are based on a specific form of CSP. The challenge is that there are many forms of CSP – called haplotypes – across regions. Vaccine efficacy, therefore, may in part depend on how closely local CSP haplotypes match those used to develop the vaccine. If they’re a close match, the vaccine should work well, but if there’s a mismatch, the vaccine may be less effective. 

A recent study in Ethiopia collected blood samples from malaria-infected children over the age of five from three health centres in different parts of the country. Of the 120 blood samples collected, CSP was successfully sequenced in 85. Whilst there was little variation in samples from the same region, there was significant variation between regions, highlighting the genetic polymorphism of CSP. Importantly, none of the Ethiopian CSP haplotypes matched the vaccine haplotype, indicating the jabs may not achieve optimal efficacy in the country.

Source

Unveiling mismatch of RTS S AS01 and R21 Matrix M malaria vaccines haplotype among Ethiopian Plasmodium falciparum clinical isolates (Scientific Reports)

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The Johns Hopkins Malaria Minute podcast is produced by the Johns Hopkins Malaria Research Institute to highlight impactful malaria research and to share it with the global community.