Army scientists have developed vaccines against two types of hantaviruses, which are known health threats to U.S. troops stationed in Europe and Asia. The research team used small amounts of genetic material, or DNA, from the Hantaan and Puumala viruses to develop the vaccines. These DNA vaccines are potentially more cost-effective, and the needle-free vaccination method used to deliver them is less painful. Dr. Connie Schmaljohn, senior scientist at the U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, discusses the research that led to the development of these vaccines and the path that lies ahead. Both vaccines are now in Phase I clinical testing, the first step toward licensure by the U.S. Food and Drug Administration.