The vaccine programme comes after the country recorded its first known case of the disease since 1994.
Guinean authorities say 58 people have been confined to their homes after being identified as contacts of a woman who contracted the Ebola virus.
The Ebola case was discovered in Ivory Coast in an 18-year-old Guinean woman who had travelled by bus from Labe, Guinea, a journey of some 1,500km (930 miles).
It was Ivory Coast’s first known case of the disease since 1994.
Ebola is often deadly, causing severe fever and, in the worst cases, unstoppable bleeding. It is transmitted through close contact with bodily fluids, and people who live with or care for patients are most at risk.
The discovery in Ivory Coast came nearly two months after the United Nations’ health agency declared an end to Guinea’s second Ebola outbreak, which started last year and killed 12 people.
“In Labe, 58 contacts have been identified,” Elhadj Mamadou Houdy Bah, the regional health director, told the AFP news agency.
“The good news is that none of them are presenting any signs (of Ebola) at the moment, all are being followed,” he added.
The driver of the vehicle that transported the young Ebola sufferer to Abidjan, Ivory Coast, is one of those identified.
As the sole centre in Labe able to handle such contact cases is currently full dealing with coronavirus patients, the Ebola contact cases were placed under confinement at home for an observation period of 21 days, the Guinean health authorities said.
An Ebola outbreak between 2013 and 2016 killed 11,300 people throughout West Africa, including 2,300 people in Guinea.
The World Health Organization (WHO) believes the toll has been underestimated.
On Tuesday, the WHO said nine Ebola contact cases had been identified in Ivory Coast, following the case of the Guinean woman there.
She is being treated in a hospital in Abidjan, while health workers are being vaccinated against the disease.
Residents of the Abidjan district where the young Guinean woman was staying are also being vaccinated.