How the current West African Ebola virus disease epidemic is altering views on the need for vaccines and is galvanizing a global effort to field-test leading candidate vaccines.

Since it first appeared as a clinical syndrome in Central Africa in the mid1970s, accompanied by isolation of the causative virus, Ebola virus disease has fascinated infectious disease clinicians, virologists, and epidemiologists because of the striking clinical syndrome exhibited by patients (which culminates in a hemorrhagic diathesis in approximately 35% of infected individuals) [1], high case-fatality rate (50%–90%), and facile transmissibility of the virus among close contacts [2], including caregivers [3]. Heretofore, its limited geographic distribution (Central and East Africa) and modest overall burden of disease, manifested as occasional small outbreaks ultimately interrupted by institution of stringent infection control methods, combined to make this an uncommon exotic tropical infectious disease [4]. After the 11 September 2001 attacks and subsequent anthrax bioterrorism episodes in the United States, there was concern in the United States and Europe over the potential use of certain pathogens as bioterrorism agents. Ebolavirus, with its high case-fatality rate and potential for enhanced transmissibility, is ranked by the Centers for Disease Control and Prevention as a category A bioterrorism agent (highest priority). This prompted virologists to study the pathogenesis of ebolavirus infection and vaccine developers to design strategies to generate vaccine candidates. During the next decade, impressive progress was made in Ebola vaccine research. However, the population targets for use of such vaccines were limited and included civilian populations in defined geographic areas, for whom reactive immunization would be performed following a deliberate release during a bioterrorism event, and laboratory scientists working with the virus.