By: Sang Hyo Kim, Staff Editor
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A new experimental vaccine, PfsPZ, offers great promise as a cure for malaria. PfsPZ demonstrated 100% success in protecting subjects from this mosquito-borne tropical disease, which affects about 200 million people and causes 660,000 death annually.1,2
Historically, it has been known that sustained immunity for malaria could be achieved by exposing human to the bites of irradiated, infected mosquitoes.3 However, such methods would take up to 1,000 bites from insects overtime to build a high level of immunity, thereby serving as an impractical method of widespread protection.2
Though there are several current vaccine trials for malaria, the PfsPZ vaccine proved to be the most remarkable. When comparing the PfsPZ vaccine to other malaria vaccines, the PfsPZ appeared to protect much more of the trial population. For example, during Phase III human trials, the leading vaccine RTS,S only showed to protect approximately one half of volunteers against malaria infection two to three weeks after the last vaccine dose, and 22%of volunteers five months after the last dose. Furthermore, when making the RTS,S vaccine, it only has a single surface of a protein from the sporozite.3 The PfsPz vaccine, however, showed a much greater success by using a whole Plasmodium falciparum sporozites, an immature stage of parasite that has been weakened by irradiation, in order to create the vaccine.3
Unlike other vaccines, which are administered intradermally and intramuscularly, PfsPZ is given intravenously. This trial examined the number of doses needed to gain full effect, and it was found that PfsPZ was most successful if four to five doses were administered. Six volunteers who were administered five doses showed 100% protection when exposed to the microscopic parasite.3 In addition, six out of the nine volunteers who were administered four doses, were protected from the disease. A major flaw in this study, however, was that there were very few participants and it is therefore difficult to extrapolate this data to the general population.3
Despite positive results, researchers are a long way from creating a vaccine. Dr. William Schaffner, head of the preventive medicine department at Vanderbilt University’s Medical School, says that future studies need to involve larger groups in field conditions, and examinations of how long the vaccines stave off infection are needed.1 Additionally, multiple intravenous doses, unlike other vaccines, requires sterile conditions, trained medical personnel, and follow-up.4 Therefore, this can become a problem when trying to administer the vaccine in countries where malaria is prevalent. Another factor that has to be considered is whether this vaccine can cover different strains of malaria. In the trial, the same strain that was used to make the vaccine was the same strain that the infected mosquitos were carrying. Regardless of these setbacks, it is important to recognize that these studies do offer promising results that we might soon have a vaccine for malaria.
SOURCES:
- S Matt and H William. U.S. reports a breakthrough in malaria vaccine. CNN health. http://www.cnn.com/2013/08/08/health/malaria-vaccine/index.html?hpt=he_c2. Published August 9th, 2013. Accessed September 1st, 2013.
- Morelle R. Malaria vaccine shows early promise in clinical trials. BBC News. http://www.bbc.co.uk/news/health-23607612. Published August 8th, 2013. Accessed September 2nd, 2013
- Mantel B. New malaria vaccine shows promise. NBC news. http://www.nbcnews.com/health/new-malaria-vaccine-shows-promise-6C10875243. Published August 8th, 2013. Accessed September 2nd, 2013
- NcNeil Jr. D. A Malaria Vaccine Works, With Limits. The New York Times. http://www.nytimes.com/2013/08/13/health/a-malaria-vaccine-works-with-limits.html?_r=0. Published August 12th, 2013. Accessed September 3rd, 2013
