Finally, a vaccine against malaria

GlaxoSmithKline has developed a malaria vaccine directed against sporozoites, the parasitic stage injected into humans by feeding mosquitoes. Theirs isn’t the only vaccine in the pipeline, but it is the first to reach phase III trials, and preliminary results look promising. RTS,S/AS01 was 50.4% (95% CI 45.8 - 54.6%) effective against falciparum malaria in 6 000 African children aged 5 - 17 months. It was 45.1% (23.8 - 60.5%) effective against severe malaria.

The trial still has a long way to go, however. Researchers recruited close to 16 000 children in two age groups, and results for younger infants aged 6 -12 weeks won’t be available for at least another year. RTS,S/AS01 was 34.8% (16.2 - 49.2%) effective against severe malaria in an analysis combining available data from both age groups.

The older children in this report had three doses of RTS,S/AS01 over 3 months, with or without a booster 18 months later. Older controls received a rabies vaccine. Younger controls were vaccinated against meningococcal meningitis group C.

A malaria vaccine has been a long time coming, and we may finally be getting somewhere, says a linked editorial. This vaccine looks reasonably effective so far, although results are too preliminary to inform policy at this stage. Safety issues to watch out for in later reports include a higher risk of febrile reactions and seizures in children given the new vaccine, and a higher risk of meningitis, which is harder to explain (11/5949 v. 1/2974 in older children; relative risk 5.5, 0.7 - 42.6).

The RTS,S Clinical Trials Partnership. N Engl J Med 2011; doi:10.1056/NEJMoa1102287

Bridget Farham


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