New malaria vaccine may offer high protection

A small clinical trial of a late liver-stage attenuated malaria parasite vaccine has been shown to be safe and effective against the mosquito-borne disease that claims 608,000 lives each year globally.

The trial, led by researchers at Leiden University Medical Center and Radboud University Medical Center in the Netherlands, found that immunisation with a genetically modified Plasmodium falciparum parasite, known as GA2, induced a favourable immune response, while also protecting against infection.

For the trial, the team randomly assigned 25 healthy adult volunteers with no prior malaria exposure to receive immunisation with a genetically modified P. falciparum parasite (GA2) — designed to continue developing longer in the liver.

While 10 participants were assigned to the GA2 group, another 10 were added to the GA1 group, and five to the placebo group. Each group consisted of both male and female volunteers.

Three immunisation sessions at 28-day intervals involved exposure to 50 mosquitoes infected with the respective parasites or uninfected in the case of the placebo group.

Three weeks after the final immunisation, all participants were exposed to a controlled human malaria infection to evaluate the protective efficacy.

The results, published in the New England Journal of Medicine, showed that protective efficacy was observed in 89 per cent of people in the GA2 group. Only 13 per cent in the GA1 group showed the protective effect, in contrast, while those administered the placebo had none.

Further, the team also found no breakthrough infections occurred after exposure to GA2, indicating a strong safety profile.

The GA2 participants also exhibited a strong proinflammatory response.

Both GA2 and GA1 induced similar antibody titers against the P. falciparum circumsporozoite protein. This suggests that the enhanced protection with GA2 is associated with cellular immune responses rather than antibody levels alone, the researchers said.