Over 1 million people a year die from malaria, and many are young children. Health officials fear that the disease will begin spreading much more rapidly, because it has developed resistance to drugs that formerly were effective -- as well as cheap enough to make widespread distribution possible.

Population growth in tropical regions adds to the number of individuals who may be at risk of contracting malaria. Half the world's population, or approximately 3.5 billion people, could be living in areas where malaria is transmitted within the next ten years, the article suggests.

The malaria vaccine RTS,S/AS02A has shown promise as a potential vaccine against Plasmodium falciparum malaria (the most severe form of the disease). It acts at the "pre-erythrocytic stage" -- that is, before the red blood cells become infected.

The phase II trial was conducted among children aged 1-4 years in Mozambique. Pedro L. Alonso of the Hospital Clinic, University of Barcelona, Spain, and Manhiça Health Research Center, Mozambique, and colleagues report on the efficacy and safety of the vaccine.

Around 2000 children were randomly allocated three injections of either the candidate malaria vaccine or other control vaccines. The children studied were in two distinct locations and had a slightly different follow up.

For children in the first cohort (around 1,600 participants), the study assessed the efficacy of the vaccine in preventing clinical episodes of malaria during a 6-month follow-up. For children in the second cohort (around 400 participants), the study assessed the effect of the vaccine on preventing subsequent new infections.

The risk of developing at least one episode of clinical malaria was reduced by 30% during the 6 months of follow up among children given the malaria vaccine compared with children given control vaccines; 58% fewer children developed severe malaria. In the second cohort, vaccine efficacy for extending time to first infection was 45%.

"Our results indicate the feasibility of development of an effective vaccine against malaria," Professor Alonso comments. "They also highlight the potential of modern vaccinology to develop new prophylactic interventions against complex human parasites," he says.

"Development of an effective malaria vaccine can be accelerated through international partnerships between private and public sectors, including scientific institutions in endemic countries," Professor Alonso continues. "In combination with existing and other promising new malaria-control measures, malaria vaccines could greatly contribute to reducing the intolerable global burden of this disease."

In an accompanying commentary, Philippe van de Perre and Jean-Pierre Dedet of the University of Montpellier, France, state: "…[R]ecent history of vaccinology tells us that vaccine development is a desperately long process. Decades are often needed from the preclinical testing of candidate vaccines to licensing and public availability.

"The current unprecedented public-private partnership for the development of malaria vaccines, with national and international agencies sharing the goals, should speed this process as much as possible and boost innovations," they say.

"The RTS,S/ASO2A manufacturer, GlaxoSmithKlineBio, might succeed in licensing this vaccine by 2010," Van de Perre and Dedet continue. "In any case, the road toward a safe and efficient malaria vaccine being available and useable on a large scale, or even incorporated into an expanded program of immunization, will be long and chaotic.

"Thus, for many decades ahead, the expansion of preventive and therapeutic strategies, including those new ones with an evident added value (e.g., insecticide-impregnated bed nets and treatment with artemisin-containing regimens) should remain an utmost priority to stop the malaria hecatomb," they advise.

"More than ever," Van de Perre and Dedet conclude, "infants, young children and pregnant women -- who are heavily affected by the direct and indirect consequences of malaria in endemic areas -- deserve a worldwide scientific, political and financial commitment. Such commitment is a question of equity, of human rights, and of disease exposure for half the inhabitants of our planet."