Two thousand kids to get experimental malaria jab

Largest ever test of malaria vaccine to begin in Africa.

9 July 2003

Tom Clarke

Malaria kills one million people a year in Africa. © WHO

The most advanced test of a vaccine against malaria ever conducted in children begins in Mozambique next week.

The hope is that immunization will become a primary weapon in the fight against malaria, which kills 1 million Africans each year, most of them toddlers and babies. Currently, drugs - to which resistance is rapidly developing - and protections like bed nets are the only ways to control the disease.

Two thousand children under five will take part in the trial, funded by the Malaria Vaccine Initiative (MVI), an independent organization based in Rockville, Maryland, which coordinates international efforts to develop malaria vaccines, and drug giant GlaxoSmithKline. "This is the largest malaria vaccine trial carried out in Africa to date," says Pedro Alonso, scientific director of the study's base, the Manhiça Health Research Centre in Mozambique.

Tests with small numbers of volunteers have satisfied researchers that the candidate vaccine - called RTS,S - is safe. The next stage, a phase 2 trial, will now ask whether the vaccine actually prevents malaria in children. Results should be available in 18 months.

RTS,S consists of a protein found on the surface of the malaria parasite at the stage when a mosquito's bite injects it into the human body. It also contains a fragment of the hepatitis B virus, too little to cause the disease, but large enough to goad the body's immune system into recognizing the malaria fragment.

A chemical mix called an adjuvant is the final ingredient. This tricks the immune system into mounting a strong immune response to the vaccine, helping it to remember the crucial parasite protein.

In tests in the Gambia, RTS,S protected up to 71% of adults from being infected with malaria. If the vaccine has similar success in children it must then pass further tests in babies. Those under a year old are excluded from this trial for safety reasons but are at the highest risk of dying from malaria.

Chances of success are slim, admits Melinda Moree, director of the MVI. Only one of 80 current malaria vaccine concepts is estimated to succeed, she explains: "We're going to hear more about failures than successes." But a clinical trial is the only way to find out what approaches do and don't work. "Even negative results move us quite a way forward," she says.

That RTS,S is in the most advanced stages of testing doesn't mean it is the best candidate vaccine. It has been in development since the 1980s and has the backing of a large company, says Adrian Hill at the University of Oxford, UK.

Hill's team is working on a different approach using modified viruses to carry malaria genes into the body; initial results are promising¹. Around nine other candidate vaccines are also in safety trials this year.

1. McConkey, S. J. et al. Enhanced T-cell immunogenicity of plasmid DNA vaccines boosted by recombinant modified vaccina virus Ankara in humans. Nature Medicine, published online, doi:10.1038/nm881 (2003).