Protection from malaria vaccine falls over time

Results from a seven-year study of the malaria vaccine RTS,S show that its efficacy falls over time. This decline is fastest in children living in areas with higher than average rates of malaria.

Findings published in the New England Journal of Medicine suggest that the benefits of the vaccine are likely to vary across different populations.

Researchers at the KEMRI-Wellcome Trust Research Programme in Kilifi, Kenya, followed 447 children who had received three doses of either RTS,S or a rabies (control) vaccine when they were between 5 and 17 months old.

During the first year of the study, the risk of getting malaria in the vaccinated children was 35.9% less than in the control group, but after seven years this protection fell to 4.4%.

In children exposed to higher than average rates of malaria, there were slightly more cases of the disease in the vaccinated group than in the control group, five years after vaccination.

This ‘rebound’ effect is thought to occur because children given RTS,S develop their natural immunity against malaria more slowly than unvaccinated children.

The researchers highlight the need for more research to determine the most effective way of using the vaccine.

Wellcome’s Head of Infections, Dr Mike Turner, said the research shows how important it is to study the impact of a vaccine over the long term, to see how protection can change over time.

"RTS,S isn’t perfect, but it still has the potential to save lives and will provide an important springboard for improved second-generation vaccines that target multiple stages of the malaria parasite's lifecycle," he added.

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