WHO leader : This vaccine could be `` the first preventive tool against Ebola in history '' This trial campaign will be conducted in a hard-hit region of the West African nation of Guinea . Authorities have had success in curbing Ebola , but dozens of new cases still arise seven months .
WHO leader : This vaccine could be `` the first preventive tool against Ebola in history '' This trial campaign will be conducted in a hard-hit region of the West African nation of Guinea . Authorities have had success in curbing Ebola , but dozens of new cases still arise each week .