Variations in malaria vaccine's effectiveness are under review

Malaria vaccine partly protects infants and children
Malaria vaccine partly protects infants and children | Courtesy of
The National Institute of Allergy and Infectious Diseases, a branch of the National Institutes of Health, recently funded a study that shows why malaria vaccines only partially protect infants and children from the virus.

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.

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National Institutes of Health

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