Health authorities in Niger said Friday they had found a fake version of a meningitis vaccine after the country had launched a campaign to innoculate millions of children against the disease.
In a statement, the health ministry asked doctors to be vigilant over a "counterfeit" version of a vaccine called Mencevax ACWY.
The fake drug is marked as having been manufactured in December 2016, with an end-date for use by November 2021, it said.
Niger launched a week-long campaign on March 5 to vaccinate six million children against meningitis, which killed nearly 200 people two years ago.
The country lies in the so-called "meningitis belt" stretching from Senegal in the west to Ethiopia in the east, where outbreaks of the disease are a regular occurrence.
The vaccination programme is against meningitis A, one of the six groups of meningitis bacteria that can cause epidemics.
The ministry's spokesman told AFP the bogus drug had been discovered during a "routine inspection" of a privately-owned pharmacy in the capital Niamey.
An investigation is underway to try to ascertain how many of the fake vaccines have been used, the spokesman said.
Health workers administering meningitis jabs are being asked to take special care about their supply source, and the public are being urged to scrutinise vaccines clearly, even if they buy them in "licensed" pharmacies.
Fake drugs -- medications that are outright counterfeits or whose active ingredients have been diluted -- are a major problem in West Africa.
In the 2017 outbreak, and in an epidemic in 2015 in which nearly 500 people died, Niger sounded the alarm over purported vials of vaccine that just contained water.
Meningitis is transmitted between people through coughs and sneezes, close contact and cramped living conditions.
The illness causes acute inflammation of the outer layers of the brain and spinal cord, with the most common symptoms being fever, headache and neck stiffness.