Malaria vaccine with chemically weakened parasite cells shows full protection at 10 weeks

An initial trial of a malaria vaccine using chemically weakened cells from the parasite which is transmitted by mosquitoes has given volunteers 100% protection against the disease, if given at a high dose.

In a trial, 67 volunteers received a placebo or low, medium or high doses of a drug called PfSPZ-CVac. They were then exposed to the early form of the malaria parasite, cells called sporozoites, between eight and 10 weeks after receiving the vaccination.

All of the people who had been given placebo and no dose of PfSPZ-CVac developed malarial symptoms, for which they were then treated. In the low-dose group, six out of nine people developed symptoms. In the medium-dose group, three out of nine people developed symptoms and in the high-dose group, none of the study participants developed symptoms.

The participants tolerated the vaccine well, and there were no side effects reported compared with the placebo group. The 0.5ml vaccine fluid was administered by direct injection into a vein three times at four-week intervals.

"By vaccinating with a live, fully active pathogen, it seems clear that we were able to set of a very strong immune response," said study author Benjamin Mordmueller of the University of Tuebingen, Germany, said in a statement.

"Additionally, all the data we have so far indicate that what we have here is relatively stable, long-lasting protection."

Last year Sanaria, the US-based biotech company developing the vaccine, published promising results with a serum called PfSPZ-Vaccine that weakened malaria sporozoites using radiation rather than chemicals. The chemical-based method could potentially convey high levels of protection at a lower cost, Stephen Hoffman, chief executive of Sanaria, told IBTimes UK.

"The advantage we have here potentially with the chemical vaccination approach is that to get the same level of protection, it looks like one requires far fewer sporozoites," Hoffman said. "The cost of goods could be much less. Trials of PfSPZ-Vaccine are currently underway in Kenya, Tanzania and soon in Equatorial Guinea."

He continued: "It's possible that this [chemical] approach is better. It definitely is more potent on a sporozoite-per-sporozoite basis. That's a huge advantage, but the radiation-attenuated vaccine will probably be used too as part of multiple approaches.

"The next steps for research on PfSPZ-CVac are to see how long the vaccine lasts, to test it in areas with natural exposure to malaria rather than in clinical conditions, and to test on multiple strains of the parasite."

The vaccines are potential future preventatives in addition to RTS,S/ASO1, which is the most advanced candidate for a malarial vaccine so far, according to the World Health Organization (WHO). There were 212 million cases of malaria globally in 2015, leading to an estimated 429,000 malaria deaths, states the WHO.