A possible risk of Ebola transmission from survivors' semen prompted the CDC to revise its advice.
The World Bank says it will provide at least $650 million to help West Africa recover.
Also ahead of economic talks, Oxfam said $1.7 billion is needed to rebuild health systems, and the World Bank shared employment data.
Guinea's progress is fragile in its fight against Ebola, with community resistance still reported in some areas.
The study of VSV-EBOV hopes to enroll 6,000 health and other frontline workers.
Though the global risk has dropped, Ebola is still a cause for concern, the WHO says.
The 30 new cases are the lowest since May 2014, fueled by improving response indicators.
Two possible next-generation Ebola vaccines fully protected monkeys with one dose.
There was evidence of Ebola virus in Liberia decades ago, according to a New York Times op-ed piece.
A 9-month boy tested positive for Ebola after he died in Sierra Leone's Kailahun district, a former hot spot for the disease that had not seen a case over the past 4 months, Reuters reported today.
