Study: Malaria Vaccine Safe, Effective for Up to 1 Year
In previous research, a team of investigators led by Robert A. Seder, MD, chief of the cellular immunology section at the National Institutes of Health, found that PfSPZ was very effective in fending off malaria for as much as 3 weeks following immunization.
Discovery Could Lead to New Malaria Treatments
Seeking to determine whether the vaccine would offer protection against malaria for a longer duration, Seder and colleagues gave it to 59 healthy adults between the ages of 18 and 45 with no history of malaria. An additional 32 healthy adults within the same age group with no history of malaria were enrolled in the study to serve as the control group, and were not vaccinated.
Those receiving the vaccine were separated into groups in an effort to establish the optimal dosage, number of vaccinations, and administration route that would offer the most effective protection. Some received 3 intravenous (IV) immunizations, with others receiving 4 immunizations. All were administered higher doses than had been previously tested in humans, the authors note, and all were exposed to bites from mosquitoes infected with malaria 3 weeks after their last immunization.
After evaluating participants’ blood samples, Seder and his coauthors found no detectable parasites in the blood of 3 of the 9 subjects receiving 3 IV doses of PfSPZ. Of the 9 who received 4 IV doses of the vaccine, 7 were found to be protected against malaria. Only 3 of the 8 participants administered 4 IV doses were protected.
The researchers enrolled an additional group of 11 patients in an effort to gauge the vaccine’s long-term protective ability, each of whom received 4 IV doses of PfSPZ and was exposed to malaria-infected mosquitoes as well, 21 weeks after their last vaccination. Overall, 6 of these 11 participants had no detectable parasites in the blood after being exposed to the parasite.
Following this, researchers then exposed 4 of these individuals, as well as 1 who had received 4 IV doses of the vaccine and had shown no detectable parasites at 3 and 21 weeks, to bites of infected mosquitoes at 59 weeks following last vaccination. None of the 5 developed parasites in their blood.
Ultimately, the authors note that administering PfSPZ provided long-term, sterile protection to a small group of patients. “This is a vaccine designed to prevent malaria infection,” says Seder, adding that “it does not treat people infected with malaria, which is done with a variety of approved drugs.”
Ishizuka AS, Lyke KE, DeZure A, et al. Protection against malaria at 1 year and immune correlates following PfSPZ vaccination [published online May 9, 2016]. Nat Med. doi:10.1038/nm.4110.