Variations in malaria vaccine's effectiveness are under review
The international group of researchers used innovative, extremely sensitive genomic sequencing technology. The vaccine in question, RTS,S/AS01 -- also known as RTS,S -- provided just moderate protection for children involved in the clinical testing.
The scientists found that the vaccine targets a specific surface protein, called the circumsporozoite (CS) protein, that has a genetic variability. This may affect the effectiveness of the vaccine. This protein is found on the surfaces of Plasmodium parasites, which cause malaria. Typically the protein has diverse genetics, meaning a wide range of variants, but the RTS,S vaccine only accounts for one variant of the protein.
There were approximately 5,000 blood samples taken from the subjects involved in Phase 3 clinical testing for the vaccine. The scientists discovered that the vaccine proved to be most effective in children between the ages of 5 months and 17 months, but only when the children were infected with parasites that shared the protein variant with the vaccine. A mismatched protein showed less protection.
Further details are available in the New England Journal of Medicine.