Juba, South Sudan — More than 1.1 million doses of an oral cholera vaccine have arrived in South Sudan, as the government launched a program to inoculate more than 80 percent of the population. But the mass vaccination exercise faces numerous challenges, including a lack of access to the areas dealing with the worst cholera outbreaks. Medics in South Sudan will attempt to vaccinate at least 9 million people against cholera, an exercise that targets mostly children and mothers. More than 1.1 million doses of oral cholera vaccine arrived in the capital, Juba, and will be dispatched next week