The 4,000 doses will be sent to the remote northwest where two confirmed Ebola cases, 20 probable ones and 20 suspected ones have been reported, spokeswoman Jessica Ilunga said.
An additional 4,000 doses will be deployed in the coming days with more available if needed, the World Health Organization said. WHO has reported 23 deaths among the 42 cases as medical teams try to contain the hemorrhagic fever in Equateur province.
Health experts have identified 500 contacts of the cases and they are now being traced, Ilunga said. She has said health workers would be among the first to receive vaccinations. Three nurses are among the suspected cases and one is among the dead.
The experimental vaccine has been shown to be highly effective against Ebola. It was tested in Guinea in 2015 during the outbreak that killed more than 11,300 people in West Africa from 2014 to 2016.
This is the ninth Ebola outbreak in Congo since 1976. While none has been connected to the one in West Africa, the experimental vaccine is thought to be effective against the Zaire strain of Ebola found in Congo.
WHO said it will use the "ring vaccination" method. It involves vaccinating voluntary contacts, contacts of those contacts and health care and other front-line workers.
Congo's health ministry announced the Ebola outbreak on May 8 after two cases were confirmed in Bikoro. The Bikoro health zone is about 150 kilometers (93 miles) from Mbandaka and 45 kilometers from Ikoko Impenge, which have suspected cases.
Associated Press reporters Carley Petesch in Dakar, Senegal and Jamey Keaten in Geneva contributed.
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