The Ervebo vaccine is licensed for use against Ebola virus, one of the viruses that cause Ebola disease, but not for Bundibugyo strain, which is responsible for the current outbreak.
The World Health Organisation said that while it was not known whether Ervebo might protect against the Bundibugyo virus, "early laboratory and animal data suggest it might provide some protection".
The allocation included 20,000 doses for a phase 3 clinical trial to understand the impact of the vaccine on the Bundibugyo virus, the agency said on Thursday.
The remaining 50,000 doses will be used for front-line and health workers as recommended by WHO experts.
The outbreak raging in eastern Democratic Republic of the Congo has killed 2476 people out of the 5208 confirmed cases since it was declared in May.
It has infected and killed more people at a greater speed than any other Ebola outbreak in history, and is spreading about three times faster than that of 2014-16 across West Africa, which was the deadliest Ebola outbreak on record with more than 11,000 deaths.
The lack of approved vaccines or treatments for the rare Bundibugyo virus has been a major issue for responders.
Also, most new cases are being reported outside of the people being monitored, showing it has spread quickly and left surveillance teams racing to catch up.
