Drugmaker Develops 100 Percent Effective Malaria Vaccine
Lawrence LeBlond for redOrbit.com – Your Universe Online
A team of scientists have for the first time developed a vaccine for malaria that has been found to be 100 percent effective in a small clinical trial. The vaccine, known as PfSPZ Vaccine, was developed by Sanaria Inc. in Rockville, Maryland and has so far been shown to be safe, generating an immune system response in healthy adults.
Publishing the results of the early-stage clinical trial in the August 8 issue of Science, researchers with the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), and collaborators at the Walter Reed Army Institute of Research, Silver Spring, Maryland, and the Naval Medical Research Center, Bethesda, Maryland, have found that the vaccine has far surpassed any other experimental malaria vaccine tested to date.
In order to further confirm these current findings, the vaccine will be tested in a larger clinical trial setting in Africa.
“The results are important because they demonstrate for the first time the concept that a malaria vaccine can provide a high level of protection,” said Anthony Fauci, director of the NIAID. He noted, however, that the team will remain cautiously optimistic.
Malaria is transmitted to humans via the bite of an infected mosquito. Once bitten, the infectious sporozoites (immature malaria parasites) works its way through the blood stream to the liver, where they begin to multiply and then spread through the rest of the bloodstream, at which time symptoms begin to materialize.
The PfSPZ Vaccine is composed of weakened sporozoites of the species Plasmodium falciparum, the most deadly of the malaria-borne parasites. By injecting these weak, but still-living parasites into the human body, patients are able to build up immunity to malaria without risk of disease.
“The global burden of malaria is extraordinary and unacceptable,” said 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.”
The World Health Organization has set an ambitious target deadline to develop a safe and effective (80 percent efficacy) by the year 2025, but until now, Fauci noted, “we have not even gotten anywhere near that level of efficacy.”
Scientists were not so sure PfSPZ was going to prove fruitful in the beginning. The reasons behind this skepticism came due to the logistical hurdles that needed to be overcome in developing an effective vaccine. To make the vaccine, Sanaria had to raise mosquitoes in sterile conditions on an industrial scale, feed them blood infected with the malaria parasite and then irradiate them to make them weaker. Once weakened, the parasites would still infect patients, but would not cause disease.
Sanaria harvested billions of parasites from mosquito salivary glands, purified them and then cryopreserved them. Many scientists, including Fauci, were highly skeptical of this process and viewed it as unsafe and unethical for creating a human medicine.
“To my amazement, Hoffman did it,” added Fauci, referring to Stephen Hoffman, a veteran malaria researcher who led the development team.
In the phase I safety trial, six subjects who were given five doses of the novel vaccine through IV were found to be 100 percent protected from malaria after receiving several bites from infected mosquitoes. In a control group, which had received no vaccine injection, five of the six sample subjects developed malaria. The researchers also found that three of nine people who were given four doses also contracted the illness.
In all, 57 volunteers were brought into the trial. Of these, 40 received the vaccine and 17 did not; only the six individuals who received five doses of the vaccine were 100 percent protected by the injection. All patients were monitored closely for seven days with no severe adverse reactions, including malaria onset, being associated with the vaccine.
During the course of the study, all patients were administered five mosquito bites from malaria-infected insects, which is a standard control procedure for malaria vaccine trials. The bites occurred three weeks after participants received their final vaccine, or received no vaccine at all.
After bites were given a chance to take effect (within seven days), all participants were admitted to the NIH Clinical Center. They remained at the clinical center until they were diagnosed, treated and cured of malaria, or were shown to be free of the infection.
In all, three of 15 participants who received a higher dosage of the vaccine became infected, 16 of 17 who received lower doses became infected, and 11 of 12 who received no dosages became infected after the round of mosquito bites.
“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.
One interesting note in the study was the method used for administering the vaccine. In previous studies using an intradermal (into the skin) and subcutaneous (under the skin) approach, immune responses were not as strong as in the intravenous (IV) approach used in this study.
Hoffman said he hopes to have a vaccine ready for the market within four years. He said the trial needs to be repeated and extended in regions where malaria is rampant to test the safety and efficacy of the drug against different strains of the parasite than what has been used in the US trial vaccine. Also, a larger trial should focus on different age groups, including children. The first African trials will be carried out at the Ifakara Health Institute in Tanzania.
Stefan Kappe, a malaria researcher at the Seattle Biomedical Research Institute in Washington, hopes the initial trial results will encourage funders to invest more money in optimizing this novel approach. “If we were talking about an HIV vaccine, there would be no question about investing in this type of success,” he noted.