Yesterday, some very exciting news was reported in Science magazine: a new kind of malaria vaccine is showing unprecedented results in an initial lab study
Fifty-seven volunteers participated in the study. Subject groups received varying numbers of doses of the new vaccine, with a control group remaining unvaccinated. Three weeks after the vaccinations, subjects were deliberately infected with malaria through the bites of five infected mosquitoes. The results were unexpectedly conclusive:
- 6 subjects, each receiving 5 doses of vaccine: 0 cases of malaria
- 9 subjects, each receiving 4 doses of vaccine: 3 cases of malaria
- 12 subjects, each receiving 0 doses of vaccine: 11 cases of malaria
In this study, subjects receiving 5 doses of the vaccine were 100% protected from the malaria parasite– an unprecedented result in the history of malaria research.
The quest for a malaria vaccine has been a long and frustrating one. The complicated life cycle of the Plasmodium
parasite has allowed it to elude scientists’ best efforts for decades, and previous vaccine trials have resulted in limited success. A goal of the World Health Organization is to produce a malaria vaccine with 80% efficacy by the year 2025. This study represents the first time a sufficiently high level of protection has been demonstrated.
The new vaccine, named PfSPZ (for “Plasmodium falciparum
sporozoite”), uses a whole, weakened Plasmodium
parasite to induce human T cells to attack the invading parasite. This technique is similar to that used in the oral polio vaccine, which has brought polio to the brink of global eradication. The PfSPZ vaccine was developed by irradiating mosquitoes infected with Plasmodium falciparum
to weaken the parasite, harvesting the parasite from the mosquitoes’ salivary glands, purifying and freezing the parasite in its sporozoite stage, and injecting the sporozoites into humans intravenously and in high doses. The PfSPZ vaccine has been deemed safe, and was well-tolerated by experimental subjects.
Experts are cautiously optimistic about the promise of the new vaccine. There are several limiting factors at the moment that make PfSPZ still a few steps removed from the sought-after “silver bullet” of a simple, effective and easy-to-deliver malaria vaccine:
- This study involved a very small test group. Sanaria is planning to stage much broader trials in Africa, beginning at the Ifakara Health Institute in Tanzania six weeks from now.
- This trial only tested the vaccine’s short term results. In order to be useful in malaria-endemic areas, a vaccine would need to demonstrate long-term efficacy. So far the long-term results of the PfSPZ vaccine are untested.
- The PfSPZ vaccine must be injected multiple times, intravenously. IV injection is more complex and time-consuming than oral or subcutaneous injection, and requires more training.
- In its present form, the PfSPZ vaccine must be kept frozen with liquid nitrogen. This could greatly limit the possibilities for distribution to rural and less-developed areas.
Even amidst these challenges, this new vaccine brings undeniable hope for the eventual elimination of malaria. Here are several news stories about the PfSPZ vaccine:
- The original study published in Science, entitled “Protection Against Malaria by Intravenous Immunization with a Nonreplicating Sporozoite Vaccine” (abstract available; must subscribe to read full article)
- From NPR’s health blog (with podcast)
- From CNN (with video)
- From Nature science journal
What do you think of this news?
– Jessica Nipp Hacker,
Coordinator, ELCA Malaria Campaign