In recent years, the world has recorded tremendous progress in the fight against malaria.
The World Malaria Report 2015 shows malaria mortality rates have fallen by 66% among all age groups and by 71% among children under five in Africa since 2000. But there is still work to do and a new vaccine developed by a US-based team is showing promising results, and could accelerate progress.
Creating the vaccine, researchers infected people with weakened, genetically modified forms of the *Plasmodium falciparum parasite* in safety trials. The weakened malaria parasite, while unable to complete its life cycle and develop into full-blown malaria, exposes the immune system to the disease and stimulates a response that could block an actual infection.
The team at the Centre for Infectious Disease Research, in Seattle, deleted three genes from the parasite so it could not infect liver cells. Ten people took part in the safety trials. No one went on to develop the disease and there were no severe sides effects to the treatment. The patients’ antibodies were then given to mice, which showed greater immunity when they were deliberately infected with malaria.
Dr. Sebastian Mikolajczak, one of the researchers, said: “The clinical study now shows that the vaccine is completely attenuated in humans and also shows that even after only a single administration, it elicits a robust immune response against the malaria parasite.”Together these findings are critical milestones for malaria vaccine development.”There are two similar approaches to “attenuating”the malaria parasite – one involves weakening it by exposing it to radiation and the other gives the patient anti-malarial drugs at the same time as infecting them.
However, an approach that uses the whole parasite may ultimately prove more effective. Sir Brian Greenwood, from the London School of Hygiene and Tropical Medicine, told the BBC News website: “It is encouraging, but this is a first step toward developing a vaccine.
It is really promising and the evidence presented here is enough for challenge studies [in which people are immunised and then infected with malaria to see if it works].”However, he cautioned that the latest approach is “not practical in the field” as it requires nearly 200 bites by infected mosquitoes. Ultimately it would have to be just an injection. Dr Robert Seder, from the Vaccine Research Centre at the National Institutes of Health, said:”This report is a major advance in malaria vaccine development by providing the first evidence that genetically attenuated *Plasmodium falciparum*parasites are safe and -immunogenic- in humans.
“Future studies demonstrating protective efficacy will be the next critical milestone for continued development of this promising vaccine approach”.