Promising Results for Malaria Vaccine Trial

Encouraging phase II results of a trial to test the efficacy of a malaria vaccine for young children is published in this weeks issue of The Lancet.

Over 1 million people a year die from malaria, many of them being young children. The emergence of resistance to previously cheap and effective drugs and population growth in tropical regions could mean that by the end of the decade half the worlds population --around 3.5 billion people -- could be living in areas where malaria is transmitted .

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, i.e., before the red blood cells become infected. Pedro L. Alonso (Hospital Clinic, University of Barcelona, Spain and Manhic_a Health Research Center, Mozambique) and colleagues report the phase II findings of the efficacy and safety of the vaccine among young children (aged one to four years) in Mozambique.

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 1600 participants), the study assessed the efficacy of the vaccine in preventing clinical episodes of malaria during a six 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 percent during the six months of follow up among children given the malaria vaccine compared with children given control vaccines; 58 percent fewer children developed severe malaria. In the second cohort, vaccine efficacy for extending time to first infection was 45 percent.

Professor Alonso comments: Our results indicate the feasibility of development of an effective vaccine against malaria. They also highlight the potential of modern vaccinology to develop new prophylactic interventions against complex human parasites. Development of an effective malaria vaccine can be accelerated through international partnerships between private and public sectors, including scientific institutions in endemic countries. 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 (p. 1380), Philippe van de Perre and JeanPierre Dedet (University of Montpellier, France) state: ...recent 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. The RTS,S/ASO2A manufacturer, GlaxoSmithKlineBio, might succeed in licensing this vaccine by 2010. 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 programm 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 conclude: More than ever, 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.

Source: The Lancet