A new vaccine against malaria has proved so successful that scientists believe mass inoculation may control the deadly disease.
Results of a clinical trial published yesterday show that a dual vaccine injected as two different forms on two separate occasions is 10 times better than conventional vaccines delivered as single shots. Scientists are optimistic a wider trial of the vaccine now in progress in west Africa will demonstrate for the first time that it may be possible to control the disease by mass vaccination.
Although anti-malaria drugs are effective, they are expensive for those countries most at risk and drug-resistant forms of the disease are on the increase. Most doctors see vaccines as the only hope.
The results of the clinical trial were from a study of volunteers in Britain who were injected with the vaccine before being infected with the most lethal strain of malaria, Plasmodium falciparum. Any volunteers who developed symptoms were quickly treated with anti-malarial drugs to prevent serious illness, the study said, published in the journal Nature Medicine.
Scientists, led by Professor Adrian Hill of Oxford University, found that the vaccinated group had a far stronger "immune response". Professor Hill said the vaccine was designed to stimulate a part of the body's immune system, called the cellular immune response, not usually targeted by vaccines.
The immune system attacks viruses and parasites in two ways: by producing antibodies that swamp the invader, or by mobilising specialised "killer" or "helper" cells that can block the invasion - the so-called cellular immune response.
"It's been quite difficult to get vaccines to work through the cellular arm of the immune system. Nearly every vaccine in use works through antibodies," Professor Hill said. "The challenge has been to get vaccines to work that way because nearly all of the vaccines that have been tried in the past have given very weak cellular immune responses, not strong enough to induce protection in humans."
The scientists developed two versions of the vaccine. One was a small molecule of DNA containing certain key genes of the malaria parasite, and the other was a virus containing the same malaria proteins.
"Using the two in combination we got immune responses 10 times stronger [than normal] and highly significant protection," Professor Hill said.