Efforts at designing effective malaria vaccines have been stifled by the variation among the different strains of the parasite, but two vaccine trials have given researchers cause for hope.
A small trial in Burkina Faso (involving only 45 children) found vaccinated children 12-24 months of age were significantly less likely to acquire malaria than those who were unvaccinated. The trial was actually designed just to test the safety of the vaccine in preparation for a larger trial, but the encouraging outcome has been a boon to the research team. An 800 person trial in Mali is now slated. In fairness, these results were published as a correspondence piece in the New England Journal of Medicine and not as a fully peer-reviewed article, however, the upcoming 800 person trial will surely be subject to heightened scrutiny and it is those results that will likely determine the future of this vaccine.
A much larger trial consisting of 6,000 children 5-12 months of age in 7 African trials showed vaccine efficacy of ~56%. This number is not great for vaccines, but with 247 million cases of malaria and 881,000 deaths every year, it could constitute a substantial reduction in morbidity and mortality. Some questions have arisen about the duration of the immunity of provided by this vaccine; will it be considered a success if yearly boosters are required? Also, it is thought to be more expensive than the vaccine studied in Burkina Faso.
In general, evaluating vaccines is challenging. Figuring out the appropriate dose, dosing schedule and required boosters is often a matter of educated guesses and inferences from data. Further, neither of these inoculations reduced the risk to zero, and the importance of insecticide-treated mosquito nets, repellents and prophylaxis are still relevant. However, given the numerous failed attempts to design an effective malaria vaccine, even imperfect candidates offer reason for optimism.