Healthcare workers in Mbandaka, the capital of Equateur Province and home to 1.2 million people, is the first to receive the vaccine, World Health Organization spokesman Tarik Jašarevi? said.
The confirmation of the first case in Mbandaka last week has raised concerns that the virus could spread faster than expected. So far, 26 people have died in the outbreak, according to the WHO.
The vaccine, called rVSV-ZEBOV, will likely be distributed to some 8,000 to 10,000 people in its first phase, Peter Salama, deputy director-general of emergency preparedness and response at the WHO.
It will be given to people who have had contact with people infected with Ebola and contacts of those contacts, Salama said.
Ebola is a virus which causes the sudden onset of symptoms including fever, fatigue and muscle pain within two to 21 days after infection. Patients suffer vomiting, rash and diarrhea, impaired kidney and liver function -- and in some cases internal and external bleeding.
An outbreak in 2014 in West Africa killed more than 11,000 people in months.
