"The (Nigerian) health authorities estimate that they need 3.2 million vaccination doses in case of a meningitis epidemic," the local branch of the UN Office for the Coordination of Humanitarian Affairs said.
Added to existing reserves, the additional doses would allow officials to immunise 2.8 million people in one of the poorest countries on earth, the UN said.
Some 75 meningitis cases, including a death, have been reported since January in four of the country's eight regions, among them the capital, the UN added.
The World Health Organisation (WHO) had warned in December of a risk of fresh meningitis outbreaks in 2016 in Africa, particularly in Niger and Nigeria, which were both badly hit last year.
The risk was deemed to be especially high in parts of Niger hit by the epidemic in 2015 where vaccination was only partially completed.
Between January and June last year, health authorities recorded 573 deaths and over 8,500 cases.
In neighbouring Nigeria, there were 557 deaths and 5,221 cases in the same period.