Malaria is caused by Plasmodium falciparum, the most deadly malaria parasite transmitted by the female anopheles mosquito and is the leading killer of children under the age of five in sub-Saharan Africa.
Trials of the experimental vaccine have shown that it provides significant protection for infants and young children - the vaccine currently known by its codename RTS,S, is the most promising vaccine yet to result from 20 years of research and has already been seen to be effective protecting adults and babies in the Gambia and Mozambique against malaria.
The RTS,S vaccine candidate is a recombinant protein that fuses a part of the Plasmodium falciparum circumsporozoite protein with the hepatitis B surface antigen molecule. Combined with a proprietary GSK adjuvant system, RTS,S induces the production of antibodies and white blood cells that are believed to diminish the capacity of the malaria parasite to infect, survive, and develop in the human liver. In addition to inducing partial protection against malaria, the RTS,S vaccine candidate stimulates a protective immune response to hepatitis B, a common infection in developing countries.
The latest trials carried out in Kenya and Tanzania, have shown for the first time that the vaccine can be given as part of the standard immunisation programme as it does not interfere with childhood vaccines against diphtheria, tetanus, whooping cough and meningitis, and still provides protection.
Scientists say this will make delivery of the vaccine much easier and less costly in Africa and if regulatory approval can be obtained, a final trial involving thousands of African children is planned for next year.
The vaccine has raised hopes of an effective weapon against one of the world's biggest killers, as there are as many as 500 million malaria infections every year, mostly in the developing world.
The Tanzanian trial involving 340 infants and showed the vaccine reduced malaria infections over six months by up to 65% in babies under one year, who are the most vulnerable.
Each infant received three doses at eight, 12 and 16 weeks and in a separate trial involving almost 900 older children in Kenya and Tanzania, aged five to 17 months, a slightly different version of the same vaccine reduced cases of malaria requiring hospital treatment by 53%.
The RTS,S candidate malaria vaccine was created in 1987. Its early development was undertaken by GlaxoSmithKline (GSK) Biologicals, the vaccine division of GSK, in close collaboration with the Walter Reed Army Institute of Research (WRAIR). In January 2001, GSK and the PATH Malaria Vaccine Initiative (MVI) - with support from the Bill & Melinda Gates Foundation - entered into an agreement to develop the vaccine for children in subSaharan Africa
The results were presented this week at the annual meeting of the American Society for Tropical Medicine and Hygiene in New Orleans and are published in The New England Journal of Medicine.
