A new malaria vaccine called PfSPZ is currently undergoing phase 1 trials and has shown high levels of protection among volunteers.
According to the World Malaria Report, the decline of malaria cases has stalled globally. Therefore, in an effort to reverse the stall, researchers are working on developing an effective vaccine for the disease. While a number of malaria vaccines are currently under investigation, none have managed to provide long-term protection. However, the Sanaria vaccine, called PfSPZ, aims to change all that.
The vaccine is based on a chemoprophylaxis approach that combines live parasites with either of two widely used antimalarial drugs. The live parasites induce an immune response, and the antimalarial drugs boost the response to the injected parasites.
The researchers injected patients with Plasmodium falciparum sporozoites. Once inside the bloodstream, these infectious sporozoites then travel to the liver and bring about the infection. The patients then received either pyrimethamine, an antimalarial that kills liver-stage parasites; or the drug chloroquine that kills blood-stage parasites. Three months later, the volunteers were exposed to either an African parasite strain similar to the one in the vaccine or a strain of the South American parasite. They received the parasites via inoculation into the venous blood, under controlled conditions.
A Promising Approach
Dr Patrick E. Duffy and Dr Stephen L. Hoffman led the trials; both of which were conducted at the National Institutes of Health (NIH) Clinical Center in Bethesda, Maryland. Results of the study are available in the journal Nature.
The lowest vaccine dose provided protection from the African variant to 22% of the volunteers who received the pyrimethamine combination. Whereas, a high vaccine dose of the combination protected 87.5% of the patients from the same variant and 77.8% from the South American parasite. Additionally, 100% of the volunteers who received the chloroquine combination were completely protected from the South American variant. Moreover, this protection lasted three months for both the high dose combinations. Thus, confirming the vaccine’s effectiveness at providing long-term protection.
According to the study authors, the results of the trial suggest the benefits of using a chemoprophylaxis approach for the development of a malaria vaccine. A Phase 2 trial for the vaccine is currently underway in Mali, a country where malaria is endemic.
Mwakingwe-Omari, A., Healy, S.A., Lane, J. et al. Two chemoattenuated PfSPZ malaria vaccines induce sterile hepatic immunity. Nature (2021). https://doi.org/10.1038/s41586-021-03684-z