Late Breaking News
Investigational Vaccine Shown Safe, Effective Against Malaria in Early Trials
BETHESDA, MD — An investigational vaccine, evaluated by military researchers, safely protects against malaria infection in healthy adults by creating an immune system response, according to the results of an early stage clinical trial published recently in the journal Science.
The PfSPZ vaccine was developed by scientists at Sanaria Inc., of Rockville, MD, with clinical evaluation conducted by researchers at the Walter Reed Army Institute of Research in Silver Spring and the Naval Medical Research Center in Bethesda, in conjunction with the National Institute of Allergy and Infectious Diseases (NIAID).
Live but weakened sporozoites of the species Plasmodium falciparum, the most deadly of the malaria-causing parasites, are used in the PfSPZ vaccine.
“The global burden of malaria is extraordinary and unacceptable,” said NIAID Director Anthony S. Fauci, MD “Scientists and healthcare providers have made significant gains in characterizing, treating and preventing malaria; however, a vaccine has remained an elusive goal. We are encouraged by this important step forward.”
The Phase I trial took place at the NIH Clinical Center in Bethesda and involved 57 healthy adult volunteers ages 18 to 45 years who never had malaria, with 40 of the participants receiving the vaccine and 17 did not.
To evaluate the vaccine’s safety, two to six intravenous doses of PfSPZ vaccine at increasing dosages were administered to various groups of participants who were monitored closely for seven days. No severe adverse effects associated with the vaccine occurred, and no malaria infections related to vaccination were observed, according to an NIH press release.
Researchers found that participants who received a higher total dosage of PfSPZ vaccine generated more antibodies against malaria and more T cells — a type of immune system cell — specific to the vaccine. To test effectiveness three weeks after participants received their final vaccination, all participants were exposed to bites by five mosquitoes carrying the P. falciparum strain from which the PfSPZ vaccine was derived. Participants were monitored as outpatients for seven days and then admitted to the NIH Clinical Center, where they stayed until they were diagnosed with malaria, treated with anti-malarial drugs and cured of infection or shown to be free of infection.
Higher dosages of PfSPZ vaccine were associated with protection against malaria infection, with only three of the 15 participants who received higher dosages of the vaccine becoming infected, compared to 16 of 17 participants in the lower dosage group. Most, 11 of the 12, participants who had not received a vaccine became infected after the mosquito challenge.
“In this trial, we showed in principle that sporozoites can be developed into a malaria vaccine that confers high levels of protection and is made using the good manufacturing practices that are required for vaccine licensure ,” said Robert A. Seder, MD, chief of the Cellular Immunology Section of the NIAID Vaccine Research Center and principal investigator of the trial.
The PfSPZ vaccine is administered intravenously — a rare delivery route for vaccines — because, based on previous studies, the more common intradermal and subcutaneous routes did not yield as strong an immune response as the intravenous route for lower doses.
“Despite this challenge, these trial results are a promising first step in generating high-level protection against malaria, and they allow for future studies to optimize the dose, schedule and delivery route of the candidate vaccine,” Seder said.
Follow-up studies planned include research to evaluate the vaccine’s different dose schedules, possible protection against other Plasmodium strains and the durability of protection. Researchers also might evaluate whether higher doses administered subcutaneously or intradermally provide the same level of protection as that found in this study.