A vaccine against malaria has shown tantalizing signs of success in a clinical trial in Mozambique. In a trial involving 2022 children between the ages of 1 and 4, the vaccine lowered the odds of developing malaria symptoms by 30%. The results are the most promising so far in the search for a vaccine against a disease that kills between 1 million and 3 million people per year. But the vaccine faces several hurdles before it could be deployed, including questions about whether it would be affordable in poor countries affected by the disease.
The vaccine was developed by a consortium led by GlaxoSmithKline (GSK) Biologicals in Rixensart, Belgium. The researchers combined several techniques that bolster the immune system's fight against the malaria parasite. One is a piece of a protein present on the parasite's surface when it first enters the bloodstream via the bite of an infected mosquito. That protein is bound to a protein fragment from the hepatitis B virus, which is particularly effective at prompting an immune response. The vaccine also contains a powerful new adjuvant, developed by GSK Biologicals, which boosts the body's legions of T cells that help fight the parasite.
The combination seemed to work, at least partially. Although it didn't prevent infection, it did seem to help prevent children from becoming sick. The 688 who received the full three doses of the vaccine were 30% less likely to develop clinical malaria in the first 6 months following the injections. It was apparently even more effective in preventing the most dangerous form of the disease, severe malaria, lowering a recipient's risk of developing the life-threatening condition by 58%. Among children between ages 1 and 2, the results looked even better: It seemed to lower the chances of developing severe malaria by 76%, according to a report in the 16 October issue of The Lancet. "These are clearly the best results we've ever seen with a candidate malaria vaccine," says Pedro Alonso of the University of Barcelona in Spain, who led the clinical trial.
Alonso notes that even partial protection against malaria could save thousands of lives every year. Combined with other prevention techniques such as bed nets and insecticides, "the vaccine could have a huge impact," he says. But he and others caution that the vaccine still must be tested for efficacy in infants. Large-scale immunization efforts in Africa target children younger than 1 year.
The trial is indeed a positive sign, says Stephen Hoffman of Sanaria, a Rockville, Maryland-based biotech company working on a different technique to develop a malaria vaccine. "It is a very exciting, encouraging result that establishes the feasibility of developing a malaria vaccine," he says. But he cautions that bed nets and other conventional malaria-prevention methods are nearly as effective. And at an estimated $10 to $20 per dose, the vaccine is much more expensive than a bed net, which typically costs less than $1.