A malaria sporozoite, similar to those used in the vaccine. [WikiCommons]
A malaria sporozoite, similar to those used in the vaccine. [WikiCommons]

The findings from two new studies have just been released describing the efficacy of a malaria vaccine, provided by the biotech company Sanaria. In the small, controlled clinical trials, the vaccine proved to be extremely efficacious and sustained effectiveness over a number of weeks. The new vaccine—called Sanaria® PfSPZ-CVac—is composed of live, attenuated, and purified malaria sporozoites and the antimalarial drug chloroquine. Results from the two studies were published in Nature in an article  entitled “Sterile Protection against Human Malaria by Chemoattenuated PfSPZ Vaccine” and in The Lancet Infectious Diseases in an article entitled “Progress with the PfSPZ Vaccine for Malaria.”  

In the Nature study, PfSPZ-CVac was administered to nine subjects three times over 8 weeks—the research demonstrated the three doses were also safe and effective when administered over just 10 days. Amazingly, the researchers report reported that all nine immunized subjects (100%) were protected against the malaria parasite Plasmodium falciparum (the most pathogenic of all human malaria strains) when exposed to the disease 10 weeks after their last vaccine dose.

Scientists verified that assays of the subjects’ cellular immunity correlated with vaccine-induced protection. A team from Antigen Discovery Inc. that studied the antibody responses of the nine protected individuals identified 22 malaria parasite proteins that could be the targets of protective immune responses. Moreover, the investigators found that from the antibody responses of the nine protected individuals, they were able to identify 22 malaria parasite proteins that could be the targets of protective immune responses.

“We are extremely encouraged by these findings,” remarked co-senior study investigator Stephen Hoffman, M.D., founder and ceo of Sanaria. “Clinical trials of PfSPZ-CVac underway in Germany, the U.S., and Equatorial Guinea, and soon to start in Mali, Ghana, the U.S., and Gabon will lead to an optimized vaccination regimen that we expect to move rapidly into Phase III clinical trials and licensure. The ability to complete an immunization regimen in 10 days will facilitate the use of PfSPZ-CVac in mass vaccination programs to eliminate the malaria parasite and to prevent malaria in travelers.”

Life cycle of the malaria parasite. [NIH]
Life cycle of the malaria parasite. [NIH]

The Lancet study reported on findings from a small randomized, double-blind trial in Mali within an area of intense malaria transmission—showing sustained protection from P. falciparum over 24 weeks. Five doses of the PfSPZ vaccine were administered to 44 subjects, and saltwater placebo was given to 44 subjects. Volunteers were followed for 6 months through the subsequent rainy season to determine the presence of malaria parasites in the blood.

While a staggering 93% of the placebo group had one or more infections, only 66% of the vaccinated subjects acquired an infection and in those vaccinated subjects who became infected, the time to infection was delayed.This represents 48% protective efficacy by time-to-event analysis and 29% efficacy by proportional analysis. The researchers reported no differences in adverse events between the vaccinated group and the placebo group.

“These are extremely encouraging results as we have seen significant protection with a dosage regimen that we know to be suboptimal,” Dr. Hoffman explained. “We are now building on the protective efficacy seen in this first, landmark study of the efficacy of the PfSPZ vaccine in Africa in current clinical trials of the PfSPZ vaccine underway in Tanzania, Equatorial Guinea, Burkina Faso, Germany, the U.S., and of course in Mali. We feel that we are moving rapidly toward establishing a dosage regimen that will provide the high-level protection needed by the billions of people at risk every day from this lethal disease.”   

African children are hardest hit by malaria, with some estimates stating one death every 5 seconds from the parasitic disease. Moreover, the World Health Organization stated that in 2015 malaria caused approximately 214 million clinical episodes and 438,000 deaths worldwide—yet other estimates have up to 730,000 malaria deaths in 2015. This enormous morbidity and mortality occur despite the investment of billions of dollars in malaria control efforts. Malaria is also a concern for tourists, diplomats, business travelers, aid workers, industrial workers, and military personnel worldwide.

“Many of us living in countries where people’s lives are devastated by malaria have been waiting decades for a highly effective malaria vaccine,” noted Ogobara Doumbo, M.D., Ph.D., director of the Malaria Research Training Center at the University of Bamako, Mali. “Over the past decade, we have studied many experimental malaria vaccines in Mali. This is by far the best result we have ever obtained. We are excited and encouraged by these new results, and are proud to have hosted the first field efficacy trial of the PfSPZ vaccine in Africa here in Mali, and are expectantly awaiting the results of our second study.”

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