New Malaria Vaccine Shows Promise, but Faces Many Challenges
A study published recently in Science called “Protection Against Malaria by Intravenous Immunization with a Nonreplicating Sporozoite Vaccine” tells how researchers for the first time successfully developed a vaccine that may provide 100% protection against malaria, a disease that kills a child every minute. However, the vaccine is incredibly difficult to develop, and to deliver it to those who need it most.
The vaccine, known as PfSPZ Vaccine, was developed by a Rockville, MD company called Sanaria, but it wasn’t easy:
1) First, the researchers had to raise hundreds of thousands of mosquitoes and get them to feed on blood that had been infected with the malaria plasmodium.
2) Next, they irradiated the mosquitoes in order to weaken the malaria while keeping the mosquitoes alive.
3) Then they employed dozens of people to employ micro-surgeries, which involved removing the malaria sporozoites from the mosquitoes’ salivary glands.
4) Finally, the malaria sporozoites were then gathered and purified and the vaccine was developed.
Although the process was difficult, the results were promising. Human volunteers were infected with malaria and given different doses of the vaccine intravenously. Only three of the 15 participants who received higher dosages of the vaccine became infected, compared to 16 of 17 participants in the lower dosage group who became infected. All six volunteers who got five intravenous doses did not get malaria when bitten by infected mosquitoes.
“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, M.D., chief of the Cellular Immunology Section of the National Institute of Allergy and Infectious Diseases (NIAID) Vaccine Research Center and principal investigator of the trial.
But despite the promises, there are still challenges:
1) Employing people to perform hundred of thousands of micro-surgeries on mosquito salivary glands is impractical and would make mass production of the vaccine nearly impossible.
2) The vaccine in this study was given intravenously, which would be difficult to administer in developing countries and in primitive conditions.
3) Like many vaccines, this one must be kept frozen. Again, this could be difficult in areas that do not have electricity or modern facilities.
4) The vaccine required five doses before it could offer 100% protection.
However, Dr. Seder said, “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.”
In the future, if new techniques are developed to harvest the sporozoites and to administer the vaccine, this could potentially save millions of lives.
A number of follow-up studies are planned, including research to evaluate the vaccine’s different dose schedules, possible protection against other plasmodium strains and the durability of protection. The researchers may also evaluate whether higher doses administered subcutaneously or intradermally provide the same level of protection as that found in this study.
Read more at: