Early stage clinical testing of Sanaria's intravenous malaria vaccine has shown promise, according to results published in Science. The vaccine, known as PfSPZ, contains attenuated Plasmodium falciparum (Pf) sporozoites (SPZ), was shown to be safe and well tolerated when administered to the 40 adult volunteers. However, it’s not the safety profile that has excited the malaria research community. The vaccine has also displayed unprecedented efficacy at protecting against malaria.
The volunteers received different doses of the vaccine and were then exposed to malaria-carrying mosquitoes. Of the six volunteers that received the highest dose – 5 doses of PfSPZ – none went on to become infected with malaria. Furthermore, only three of the nine volunteers who received 4 doses of the vaccine went on to contract malaria. This is in contrast to five out of the six unvaccinated volunteers who become infected with malaria.
On the face of it, it could be said that the vaccine was 100% effective at the highest dose – although the trial was of course too small to draw any firm conclusions. While many of the current experimental malaria vaccines target parts of the P. falciparum parasite, Sanaria's vaccine uses a weakened form of the whole parasite to induce a broad response against many different targets.
“We were excited and thrilled by the result, but it is important that we repeat it, extend it and do it in larger numbers,” said lead author Dr Robert Seder, from the Vaccine Research Center at the National Institutes of Health. "It allows us in future studies to increase the dose and alter the schedule of the vaccine to further optimise it. The next critical questions will be whether the vaccine is durable over a long period of time and can the vaccine protect against other strains of malaria.”
To make the vaccine, Sanaria raised mosquitoes in sterile conditions, infected them with the malaria parasite, and then weakened the parasite through irradiation. The parasites were then harvested from the salivary glands of the mosquitoes.
“While we’re still in the early stages of testing, we believe this vaccine will be used to eliminate malaria,” said Stephen L. Hoffman, CEO of Sanaria. “It’s reasonable to suggest that within three-to-five years, a safe, reliable vaccine could be a commercial reality and provide medical benefit to a huge population.”
Of course, the vaccine was administered intravenously. Could this be an issue if and when it comes to delivering the vaccine in a mass campaign?
If you want to know more about strategy and innovation in vaccines, you might be interested in attending the World Vaccine Congress Europe 2013, 16-17 October 2013, Lille.