For healthy adults from Sierra Leon, the recombinant type-5 vector-based Ebola vaccine is safe and immunogenic, according to a study published online Dec. 21 in The Lancet . Feng-Cai Zhu, from the Jiangsu Provincial Center for Disease Control and Prevention in Nanjing, China, and colleagues recruited healthy HIV-negative adults aged 18 to 50 years, with no history of Ebola virus infection and no previous immunization with other Ebola candidate vaccines.