Children sick with malaria, rest on blankets in Jandemar, Sierra Leone.
Preliminary results from the trial of a malaria vaccine show that it protected nearly half of the children who received it from bouts of serious malaria, scientists said Tuesday.
The vaccine, known as RTS,S and made by GlaxoSmithKline, has been in development for more than 25 years, initially for the American military and now with most of its support from the Bill and Melinda Gates Foundation.
The clinical trial is scheduled to continue through 2014 and will include tests on more than 15,000 children, from infancy on up. Early results released at a Seattle malaria conference on Tuesday showed that three doses protected 47 percent of the 6,000 children ages 5 months to 17 months from severe malaria. (The age group was chosen because newborns have some protection from their mothers’ antibodies.)
“The results are encouraging, but we still have a way to go,” said Dr. Tsiri Agbenyega, who heads malaria research at a Ghanaian hospital that was one of the 11 research sites. He announced the results, which are being published in The New England Journal of Medicine.
While 47 percent protection is not very effective — most vaccines are not released until they do better than 90 percent — the chief executive of Glaxo, Andrew Witty, noted that even that much protection would save millions of lives over a decade.
Malaria is estimated to kill about 780,000 people a year, most of them African children. Adults who survive those childhood bouts usually develop at least partial immunity.
A few years ago the World Health Organization estimated that malaria killed one million people a year, and in 2008 it said that mosquito nets, DDT and newer artemisinin-based drugs paid for by donor nations were making a dent. But the estimates are controversial and change when new statistical methods are applied. Also, malaria can bounce back frighteningly fast as soon as control measures are relaxed or even in hotter, wetter weather.
It is far harder to make a vaccine against parasites like malaria than to make one against a virus. The malaria parasite changes shape as it moves from blood to liver and back to the blood, and each form has different surface proteins.
Glaxo has already spent more than $300 million on RTS,S, which will probably be named Mosquirix if it is introduced commercially, and expects to spend up to $100 million more, Mr. Witty said. Then, if the vaccine is approved, the company will make it at cost plus 5 percent for poor countries, with the 5 percent profit plowed back into malaria research.
Asked whether the Gates Foundation would pay for a vaccine that is less than 50 percent effective, Dr. Regina Rabinovich, the foundation’s chief of infectious diseases, said: “Would I prefer to see 100 percent efficacy? Obviously. But I look forward to the 2014 results, and any decision we make will be data-driven.”
Many rival malaria vaccines, targeting different surface proteins or using different methods to provoke the immune system into a counterattack, are in development. Some researchers have suggested combining several in one shot or giving sequential shots of different ones to see if combinations do better.
“That could be a possibility, but it is not in the works now,” said Dr. Christian Loucq, director of the PATH Malaria Vaccine Initiative, which coordinated the RTS,S trials and is overseeing some other vaccines that the Gates Foundation is backing.
The field’s most pessimistic experts argue that making a long-lasting malaria vaccine is impossible because even the “perfect natural vaccine” — surviving repeated bouts of malaria — fades after a few years away from the malarial area.