Malaria: Three-dose Plasmodium falciparum sporozoite (PfSPZ) vaccine shows safety, efficacy in Burkina Faso adults

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A three-dose regimen of a whole-parasite malaria vaccine — called Plasmodium falciparum sporozoite (PfSPZ) vaccine — has shown safety and efficacy when tested in adults living in Burkina Faso, West Africa, which has endemic malaria. This is the finding of a new study published December 7, 2022, in Translational Medicine Sciences. The work was led by researchers at the University of Maryland School of Medicine’s Center for Vaccine Development and Global Health.

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About 241 million people worldwide contracted malaria in 2020, and 627,000 people died from the infection. Scientists have tried for decades to develop a highly effective malaria vaccine without much success. This is because vaccines have been shown to provide little protection for those who already contracted malaria early in life due to their acquired immunity. The first vaccine against malaria (RTS, S/AS01) was approved by the World Health Organization in October 2021 and provides modest protection against malaria.

The new study included 80 participants in a randomized, controlled clinical trial comparing three doses of the PfSPZ vaccine with a placebo. After six months of follow-up, the vaccine’s efficacy reached 48 percent; After 18 months of follow-up, the vaccine’s efficacy was up to 46 percent.

“Our study shows that the vaccine can be administered to adults with malaria in a severely endemic area and still provide protection, which is challenging and complex because these individuals already have significant immune responses to malaria parasites that would have to be overcome with a vaccine,” said study author Matthew B. Lawrence, PhD. Medicine, MPH, Professor of Pediatrics at UMSOM and Director of the International Clinical Trials Unit in the Malaria Research Group at CVD.

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The PfSPZ vaccine consists of a live, attenuated form of the malaria parasite Plasmodium falciparum sporozoite, which is transmitted by mosquitoes. The vaccine was manufactured by Sanaria Inc. Based in Rockville, Maryland, it has been shown to provide at least 90 percent protection in challenge studies where volunteers contract malaria (in a highly controlled manner); These studies were conducted by CVD researchers in the United States and other groups in Tanzania. For African adults who were previously infected with malaria, PfSPZ delivered a vaccine efficacy of 52 percent against naturally transmitted malaria infection. Protection lasted from 8 to 14 months.

In the new study, the researchers wanted to reduce the number of injections required from five shots to three, while improving the effectiveness of the vaccine. They evaluated the safety, tolerability, immunogenicity, and efficacy of the vaccine for three injections of the vaccine in a two-part study.

Part one enrolled 32 adults in the dose-escalation phase in 2016, and the second enrolled 80 adults in a randomized trial in 2017. In the randomized trial, 39 subjects received PfSPZ vaccine and 41 received placebo. The study participants were healthy men and non-pregnant women between the ages of 21 and 40. The vaccines were well tolerated and free of side effects.

“New strategies are needed to achieve the United Nations Sustainable Development Goal of reducing malaria incidence and mortality by 90 percent by 2030,” said UMSOM Dean Mark T. Gladwin, MDAnd Vice President for Medical Affairs, University of Maryland, Baltimore, and John Z. and Ikeko Powers Distinguished Professor. “Innovative vaccines that provide a higher level of protection against malaria are urgently needed to help achieve this goal.”

The new study reflects a long history of malaria vaccine development at UMSOM that began in the early 1970s with landmark research from David Clyde, MD, former chief of malaria studies at CVD. His studies showed that a high level of protection against malaria infection is possible with a whole organism vaccine.

Future research includes conducting additional clinical trials of the PfSPZ vaccine in populations that would benefit most from the protection induced by the vaccine, including children, travelers, military personnel, and pregnant women.



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