After 40 years of research and clinical testing, one of the great challenges of medicine looks as if it may be on the way to a solution: an anti-malaria vaccine, RTS,S, is currently undergoing clinical trials and showing promising results.
No-one claims that the battle against the disease – which kills about one million people a year – has been won. But of the 20 or so vaccines under development, testing of RTS,S is at the most advanced stage. Some 16,000 children aged between five and 17 months are taking part in phase III clinical tests in seven African countries. Initial results indicate that it halves a child’s likelihood of falling ill with malaria.
Knowing that most anti-viral vaccines are nearly 90 per cent effective, the figure might seem disappointing. But malaria is caused not by a virus, but by a parasite. Parasites change their skin much faster than virus and bacteria do; the anti-malaria vaccine will be the first to offer protection against any parasitic disease.
Despite these reservations, Genton and Pécoul agree that the vaccine represents an important victory in the fight against malaria. There is still a long way to go, but it is a major first step towards another vaccine, or a modified vaccine, which will be more effective.
Three approaches
The parasite is tenacious. It probably first infected human beings when they started to live in settled communities more than 10,000 years ago. The most dangerous form of the micro-organism responsible for malaria, plasmodium falciparum, learned long ago how to deceive its host’s immune system.
But once it has taken up residence inside the body, the parasite needs help before it can move on to its next victim. This is where the female anopheles mosquito comes in: she ingests the parasite when she takes a blood meal from an infected person.
After passing through various stages of its life cycle within her body over a period of about ten days, it is ready to be passed on to the next human being she bites.
There are three fronts on which the disease can be fought. One is to eliminate the mosquitos, or to stop them biting (for example through the use of mosquito nets permeated with insecticide); the second is to treat everyone who has been infected, to prevent the parasite from being passed on; and the third is to vaccinate those who have not yet been infected.
So the vaccine is not a panacea, but rather an addition to the current strategies for ridding the world of malaria.
nassirtendegu 