Around 252 were killed in the meningitis epidemic in eight districts of poverty-stricken Niger.
"As of May 3, 252 people died out of a total of 3,304 cases," said Niger's epidemics surveillance and response director Goumbi Kadade.
Less than two weeks ago, the government had put the toll at 129 people out of 1,150 cases.
A meningitis epidemic has been declared in eight districts of Niger, while three others are in a state of alert, the official said.
The whole of Niger is currently under quarantine, in an effort to contain the highly contagious disease.
Some 300,000 vaccine doses have arrived in the west African landlocked country, and are currently being distributed.
That is less than half the amount the authorities ordered, and far below the 1.8 million doses actually needed to stop the epidemic, Kadade said.
One reason for the vaccine shortage is a meningitis epidemic in northern Nigeria, near Niger, the doctor said.
The epidemic's mortality rate in Niger has shrunk in the past weeks, because patients are now being given antibiotics, he added.
Niger, one of the world's poorest countries, is prone to meningitis epidemics.