A new review of malaria vaccine trials has found one kind of vaccine that holds real promise for combating this ancient disease. Epidemiologist Patricia Graves examined a collection of previously published studies to analyze which of the vaccines being tested in humans works best.

In one study, an experimental vaccine called RTS,S was given to men in The Gambia. The men got a booster shot one year later. The Gambian men had about a 65 percent reduction in malaria attacks after both doses. Graves looked at another trial of the same vaccine with 5 to 9 year olds in Mozambique, and reports, "There was about a 25 percent reduction in clinical malaria attacks in the vaccinated children. But most importantly, there was a more than 50 percent reduction in the number of severe malaria attacks in the vaccinated children compared to children who received placebo." That reduction is important because malaria is especially deadly in children.

Usually, when scientists create vaccines, they want something that is much better than 50 percent effective. But malaria is caused by a parasite, so it's different than other diseases, and Graves explains that's part of the problem with finding a vaccine. "Malaria is a much more complicated organism than the usual things we vaccinate against, like measles or DPT, which are [caused by] viruses, or bacteria that [are] easier to prevent against."

Some scientists now believe that an effective malaria vaccine will be a combination of several vaccines, none of which is completely effective on its own.Graves published her review as part of the Cochrane Collaboration. The organization's volunteer researchers synthesize results of clinical trials and published studies to come up with clinical recommendations. Graves says it's a valuable approach. "This is a way of presenting all the information at once, and allowing it to be appraised comparatively. You can look at the aggregated data that's accumulated over time and see a trend emerging." She adds that looking at data this way also allows researchers to focus their attention on more successful treatments that warrant further study.