War against malaria gets a shot in the arm

The new vaccine provided the best result so far of any tested in the field swissinfo.ch

Scientists from Switzerland, Australia and Papua New Guinea have achieved significant results in trials of a candidate malaria vaccine. They say it could offer hope to the 300 million people who suffer from acute malaria every year.

The Swiss Tropical Institute in Basel has participated in the testing in Papua New Guinea of a vaccine developed in Australia.

Following successful trials on adults, about 120 children from a remote area of Papua New Guinea were selected for the tests.

“These children were followed for about two months to see if they had the parasite in their blood,” said Dr Blaise Genton, a clinical epidemiologist and specialist in tropical medicine, who works in Basel and Lausanne.

“We observed that the vaccine was safe and that it reduced by 62 per cent the parasite density in the children who had been vaccinated, compared with those who had received a placebo. It’s the best result so far with a malaria vaccine tested in the field.”

Immune response

The candidate vaccine consisted of three different proteins or antigens which trigger an immune response. The test proved for the first time that the vaccine had a specific effect on one particular strain of parasite.

Genton said vaccines based on a variety of proteins would therefore have to be developed to knock out all the strains of malaria.

Malaria kills over one million people each year and threatens around 40 per cent of the world’s population, mainly in developing countries. Most malaria deaths are among children under five years of age.

It is not yet known how the candidate vaccine will work in younger children who have less immunity and are more prone to malaria diseases.

“We’re really working a bit in the dark,” Genton told swissinfo. “We know that people progressively develop some immunity against malaria. When they get older, they get less sick and mortality rates drop. We know there is something in the immune system that works but we don’t know exactly what.”

Parasite infection

Scientists are concentrating their efforts on creating a malaria vaccine, which limits the ability of the parasite to successfully infect large numbers of red blood cells. It would not prevent the infection but it would limit the severity of the disease and help prevent malaria deaths.

While vaccines can prevent many viral and bacterial infections, a successful vaccine has yet to be developed against a complex multi-cellular parasite like the one which causes malaria.

“A malaria vaccine will not have a 95-99 per cent success rate like the measles vaccine because parasites are different from viruses,” said Genton. “The parasite will always try to evade the immune responses of the host, so developing a malaria vaccine will be much more difficult and it will never be as effective as viral vaccines.

“If you have a vaccine that will halve the cases of malaria and will reduce the number of malaria-related deaths, that is already an important development.”

by Vincent Landon