Even getting this far took decades of research and a $300 million investment on GSK’s part, not to mention financial commitments from sponsors of the multicenter trial, which spans seven African countries. The vaccine is the first against a parasite, an organism that tends to be more complex than the bacteria and viruses that can cause infectious diseases. The malaria parasite, Plasmodium falciparum, also adopts a complicated life cycle once inside a human host in order to protect itself from destruction by the immune system. Once introduced into the bloodstream through bites from mosquitoes that carry the bug, P. falciparum immediately targets the liver, where it reproduces and sends a more streamlined form to infect red blood cells.
The RTS,S vaccine is designed to intercept P. falciparum‘s journey to the liver by binding it to antibodies that prevent it from reaching the organ; once the parasite infects the liver, it’s difficult to extract. “In the liver, they can escape the immune system, so there is only a short period of time during which the antibodies can act,” says Loucq. “So we need a high level of antibodies to be sure they will act during the short period of time before the parasite reaches the liver.”
Work on the vaccine can be traced back to the 1960s, when researchers at New York University first identified the portion of P. falciparum that would make a good target for vaccine-delivered antibodies. It’s taken decades of research, however, to act on that information and find the right section of the parasite’s coat that the bug doesn’t easily change to bypass a vaccine.
And it will take several more years to gather enough data to support the safety and efficacy of the vaccine, as well as work out how the inoculation will be distributed in public health programs in developing countries. GSK’s CEO Andrew Witty has committed to investing another $50 to $100 million to see the research project through and to supplying the vaccine at the lowest possible price to those most in need. A 5% profit the company plans to build into the price of the drug will be re-invested in neglected-disease research, and Witty said the company would forgo its profits on the vaccine.
But even if the vaccine proves effective and can be distributed at a reasonable price, public health experts stressed that it shouldn’t be the final and only answer to fighting malaria. The study participants were also using existing malaria interventions, such as insecticide-treated bed nets, and taking part in indoor spraying for mosquitoes. These preventive measures should remain an important part of keeping rates of the disease down. “It’s very important that when the vaccine is deployed, that it’s deployed with proven interventions of malaria control,” Dr. Mary Hamel of the Centers for Disease Control and Prevention’s malaria branch said during the briefing. “This trial was conducted in the setting of good control measures, and showed added benefit with those measures in place. And it’s how we should expect such a vaccine would be deployed at this time.”
Whether the new malaria vaccine will indeed make its way onto the childhood immunization schedule for children in developing nations won’t be clear for another few years. But the current results are a promising step in the right direction.