Tamar Kahn
18 October 2007
Cape Town — Tests on GlaxoSmithKline's RTS,S candidate malaria vaccine show that it is safe and reduces infection in very young African babies, offering hope that a vaccine protecting children against the disease is within reach, scientists announced this week.
Malaria is caused by a mosquito-borne parasite, and kills more than one-million people each year, mostly in sub-Saharan Africa and among children under five.
In a study published online by the Lancet yesterday, scientists reported that Glaxo's vaccine reduced the risk of malaria infection in babies by 65% and cut the number of cases of full blown malaria by 35% in babies aged between 10 and 18 weeks, the group most vulnerable to the disease.
"We are very encouraged by the results , but a good deal of work is required before we meet our goal," said the study's principal investigator Pedro Alonso, director of the Barcelona Centre for International Health Research at the University of Barcelona.
The phase II clinical study involved 214 babies in rural Mozambique, 50km north of the town of Manhica, where malaria is rife. It built on research published three years ago showing that the candidate vaccine was safe and offered some protection to slightly older children, aged between one and four.
"In rural areas, clinical malaria cases are often missed -- by the time parents realise it's not flu, it may be too late. Blocking infection before it even starts would be a tremendous advance and that is exactly what this vaccine appears to do," Alonso said in a teleconference call from Seattle, where the Bill and Melinda Gates Foundation is hosting a malaria meeting this week.
Glaxo's RTS,S product is the most advanced malaria vaccine in development, but scientists warned that it would still be several years before there was conclusive evidence that it was safe and effective. Licensing is not expected before 2011. A phase III trial designed to demonstrate the vaccine's safety and efficacy is due to start in the second half of next year. It will be one of the largest clinical trials run in Africa, with 16000 participants in 10 sites in seven countries, said W Ripley Ballou, vice-president for Global Clinical Research and Development at Glaxo's vaccine division GSK Biologicals.
Two thirds of the children will get the vaccine when they are aged between five and 17 months, and the rest will get the jab as part of their routine immunisations within weeks of birth. This will help scientists figure out the best age to administer the vaccine.
Glaxo has invested more than $320m in developing RTS,S with the US Walter Reed Army Research Institute over the past 15 years. The vaccine prompts the body to make antibodies that attack the plasmodium falciparum parasite as soon as it enters the blood stream, as well as triggering T-cells to attack any parasites that enter the liver. The combined effect of these two mechanisms means very few parasites emerge from the liver to start the deadly cycle in the red blood cells, so even if a person does get infected, the disease's severity is reduced.
The vaccine is not expected to provide complete protection against malaria, but it could be the "cornerstone of the malaria fighting toolkit," said Regina Rabinovich from the Gates Foundation.
Other malaria prevention efforts would need to continue.
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