Washington — U.S. government health researchers report some success in early human testing of a malaria vaccine. In a trial involving fewer than 60 patients, the vaccine cleared three important hurdles: it’s safe for humans; it produces an immune response; and it offered malaria protection in adults.
Sanaria Inc., a biotechnology firm in Maryland, developed the vaccine in pursuit of its corporate mission devoted to cracking this scientific puzzle. The National Institute of Allergy and Infectious Diseases (NIAID), with collaborators from the Walter Reed Army Institute of Research and the Naval Medical Research Center, evaluated the Sanaria product at the National Institutes of Health (NIH) near Washington.
Fifty-seven healthy adults consented to be in what is called a Phase 1 trial. Among the volunteers, 40 participants received the vaccine and 17 did not. Making sure a vaccine is safe is one of the key objectives in a trial at this stage, so after the volunteers were vaccinated intravenously, the researchers let a week pass to see if adverse reactions emerged, or if any signs of malaria were induced by the vaccine.
The trial vaccine is known as PfSPZ, after Plasmodium falciparum, the most deadly of the malaria-causing parasites. PfSPZ is made from live but weakened sporozoites, the offspring of the infective malaria spores. The NIAID volunteer patients showed no signs of the disease itself over that first week, and developed varying levels of antibodies against malaria, depending on the level of the PfSPZ dose they received.
Three weeks after volunteers received their final vaccination, the researchers let the malaria-carrying mosquitoes loose, and participants were bitten by the insects. Deliberate human malaria infection under controlled conditions is a standard process in malaria vaccine trials, according to the August 8 NIAID press release about the test.
Twelve of the participants who received the higher doses of the vaccine did not get malaria. Three of the high-dose volunteers did come down with the disease, but that compares to infection among 16 of 17 participants in the low-dosage group.
Another 12 participants received no vaccine at all, and 11 of those volunteers came down with malaria.
“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 Dr. Robert A. Seder, the principal investigator of the trial at the NIAID Vaccine Research Center.
The volunteers were all in the NIH Clinical Center as researchers waited for symptoms to appear. The participants remained there through diagnosis and treatment with anti-malarial drugs. They were all shown to be free of infection at the end of the trial.
Seder said the trial is a “promising first step in generating high-level protection against malaria.” Future studies, he added, will attempt to find the best dosage, schedule and delivery method for PfSPZ. In the Phase 1 trial, patients got the vaccine intravenously, not a common route for vaccine. A vaccine that requires injection in a vein is more complex to administer, especially considering some of the rural and underdeveloped regions where malaria inflicts the greatest suffering.
“The global burden of malaria is extraordinary and unacceptable,” said NIAID Director Dr. Anthony S. Fauci. “Scientists and health care 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.”
In 2010, some 219 million cases of malaria and an estimated 660,000 malaria-related deaths occurred globally, according to World Health Organization (WHO) statistics issued earlier this year. The majority of malaria deaths occur among African children, age 5 years and younger.
The NIAID vaccine trial is just one of many activities backed by the U.S. government to lessen the burden of this disease. The President’s Malaria Initiative (PMI) works in 19 focus countries in sub-Saharan Africa and Asia’s Greater Mekong subregion. For the last seven years, PMI has worked in concert with national governments; The Global Fund to Fight AIDS, Tuberculosis and Malaria; the World Bank and other donors to reduce the occurrence of the disease, which research has shown contributes to a generational cycle of poverty. WHO’s 2012 World Malaria Report offered evidence of success in the anti-malarial campaign, with the estimated annual number of global deaths falling by more than one-third since 2000.