The Obstacles to Developing and Testing West Nile Vaccines for Humans

West Nile virus vaccines for humans haven't progressed beyond phase one or two clinical trials. The unpredictable nature of disease outbreaks and changing epidemiology makes it difficult to select the geographic location for a trial. It could take years to complete the trial to demonstrate clinical efficacy, so this has certainly been a deterrent in trying to design large clinical trials for West Nile vaccines.