Positive steps forward in malaria prevention
having a protective vaccine with the reporting of encouraging new
data on a candidate developed by GlaxoSmithKline Biologicals.
The results of the largest paediatric safety and efficacy clinical trial of a potential malaria vaccine conducted in Africa, were presented at a press briefing late last week, alongside their publication in The Lancet (16 October issue).
The proof-of-concept study found that GSK Bio's Mosquirix (RTS.S/AS02A) malaria vaccine candidate protected a significant percentage of children against uncomplicated malaria, infection and even severe forms of the disease for at least six months. This trial also re-confirmed the vaccine's safety in one- to four-year-old children. However, further efficacy studies will be needed before the company can consider filing for approval of the vaccine.
The data suggest that the vaccine's efficacy against clinical malaria attacks was 30 per cent. Efficacy against primary infection with Plasmodium falciparum, the parasite that causes the greatest number of cases of malaria in Africa, was 45 per cent and it provided 58 per cent protection against severe disease.
"This is really fantastic news," said Victor Nussenzweig of New York University School of Medicine in the US, who conducted research that led to the development of Mosquirix . The NYU team identified the circumsporozoite (CS) protein that forms the basis for some 15 malaria vaccines that now are in clinical trials or in preclinical testing.
"It is the first time that a vaccine has been shown to protect against severe malaria, which is a major cause of death in children in Africa. It is not yet an ideal vaccine because it is expensive, requires three doses, and it isn't known yet how durable the vaccine's protection will be, but it is a very big step forward," he added.
The double blind, controlled trial involved 2,022 children in southern Mozambique and was conducted by the country's Centro de Investigacao em Saude da Manhica.
The vaccine is directed against the sporozoite form of P falciparum. The sporozoite is the stage in the malaria parasite's lifecycle in which it is injected into humans or other animals by infected mosquitoes.
"It will still take some years before this vaccine becomes a reality, but the commitment is certainly there," noted Jean Stephenne, general manager of GSK Bio.
"We are very encouraged by these results. They demonstrate that a Plasmodium falciparum malaria vaccine based on the circumsporozoite protein is feasible. Such a vaccine could have a major impact on public health," he added.
In 2000, GSK Biologicals and the Malaria Vaccines Initiative entered into a partnership to develop the vaccine for children. The MVI was started in 1999 with a grant from the Bill & Melinda Gates Foundation, worth $150 million, which made this collaboration possible.
The vaccine takes the form of a recombinant protein that fuses a part of the P falciparum circumsporozoite protein with the hepatitis B surface antigen molecule.
Among infectious diseases, malaria is one of the world's biggest killers and is estimated to result in one to three million deaths in the world's poorest countries every year, as well as killing more children in sub-Saharan Africa than any other infectious disease.
Due to the need for further studies, a licensed malaria vaccine is not expected to be commercially available before 2010, by which time it is projected that half the world's population, or 3.5 billion people, will be living in areas in which malaria is transmitted. The economic costs of the disease for Africa alone are equivalent to $12 billion annually, it is estimated.
