An experimental malaria vaccine called PfSPZ is showing promise after it was found to have blocked the disease in early clinical trials, according to a new study published by Science magazine on Thursday. Researchers are calling the vaccine a breakthrough while also cautioning that PfSPZ isn't ready for prime time just yet. The vaccine, which is made using a weakened form of the disease, was administered in varying doses to a group of more than three dozen volunteers. Six people, each of whom were given a full five doses of the vaccine, were unable to contract malaria when exposed to the disease, the study says. This is the first time any vaccine has achieved 100% effectiveness in any trial, researchers report.

Nine others were given four doses of PfSPZ, three of whom became infected in the trial. Of another 12 who took part in the trial but weren't given the vaccine, 11 contracted malaria, the study says. The trial — which included testing handled by the National Institutes of Health, the US Army, and the US Navy — is a first step in figuring out just how safe and effective the vaccine might be. For one thing, PfSPZ needs to be tested on a greater number of people, and researchers aren't sure as of yet how long the vaccine will be effective for. The vaccine is also only currently available by way of intravenous injection (IV), which makes it more difficult to get to people than a shot or a pill.

Huge potential, but questions remain

Still, Stephen Hoffman, the CEO of the biotech company that developed PfSPZ, is hopeful. "We have demonstrated for the first time in the history of malaria that one can completely protect individuals against malaria infected mosquitos," he told NPR. According to CNN, Malaria infects more than 200 million people each year, and it claimed the lives of 660,000 in 2010. The disease is particularly rampant in developing nations. From here, Hoffman's company, Sanaria, will test out the vaccine in larger trials in Tanzania and other parts of Africa, NPR said. If all goes well, the earliest PfSPZ could make it to market would be late 2017 or early 2018, Hoffman said.