Novel Malaria Vaccine Shows Strong, Lasting Protection in Phase 1 Trials

At the highest dosage, PfSPZ conferred protection for 3 months.

Two recent Phase 1 clinical trials conducted by the United States National Institutes of Health (NIH), in collaboration with the National Institute of Allergy and Infectious Diseases (NIAID), have shown that a novel malaria vaccine candidate confers high levels of durable protection against the disease.

Results from the trials were published in the journal Nature.

“We are encouraged by the significant findings reported in this seminal paper, which justify our investment in Sanaria and its systematic, scientifically sound approach to developing the highly protective, cost effective vaccines required to eliminate malaria, a scourge of humanity, particularly for the most underserved on our planet,” Holm Keller, co-managing director of the EU Malaria Fund said.

The vaccine, called PfSPZ, was developed by the biotechnology company Sanaria. The therapy is composed of sporozoites, the form of the malaria parasite transmitted to people by mosquito bites.

In the trials, healthy adult volunteers received PfSPZ along with either pyrimethamine, a drug that kills liver-stage parasites, or chloroquine, which kills blood-stage parasites.

After 3 months, the participants were then exposed to either an African malaria parasite strain that was the same as that in the vaccine (homologous challenge) or a variant South American parasite (heterologous challenge) that was more genetically distant from the vaccine strain than hundreds of African parasites.

Findings from the trials showed that at the lowest dosage, the vaccine gave only modest protection. However, at the highest dosage, 7 out of 8 volunteers were protected from homologous challenge, and 7 out of 9 volunteers were protected from heterologous challenge.

Additionally, In the chloroquine combination, all 6 volunteers who received the higher dosage were completely protected from the heterologous challenge. Protection with the higher dosage was also seen to last for 3 months.

“These results represent extremely important progress, unanticipated by most malaria experts,” Martin Grobusch, head of the Center of Tropical Medicine and Travel Medicine at Amsterdam University Medical Centers said. “Until recently, malaria vaccine developers sought to achieve high-level protection against non-variant malaria parasites, often only two to three weeks after vaccination, with immunity waning thereafter. The finding of 100% protection against variant parasites that are so divergent from the vaccine parasites at three months is unprecedented. This vaccine approach should be advanced now as a potential tool to protect travelers to Africa and further developed for the prevention of malaria in African populations.”