A new polio outbreak in Sudan has been linked to the oral polio vaccine that uses a weakened form of the virus.
News of the outbreak comes a week after the World Health Organization (WHO) announced that wild polio had been eradicated in Africa.
The WHO linked the cases to a strain of the virus that had been noted circulating in Chad last year and warned that the risk of spread to other parts of the Horn of Africa was high.
In a statement on the new cases, the WHO said two children in Sudan, one from South Darfur state and the other from Gadarif state, close to the border with Ethiopia and Eritrea, were paralysed in March and April. Both had been recently vaccinated against polio.
The WHO said initial outbreak investigations showed the cases were linked to a continuing vaccine-derived outbreak in Chad that was first detected last year and is now spreading in Chad and Cameroon.
While so-called vaccine-derived polio is a known risk, the emergence of these cases so soon after the announced eradication of wild polio in Africa is a setback.
At issue is the fact that the oral polio vaccine – preferred in some places because of its ease of delivery and the lack of need for sterile syringes – uses an attenuated or weakened version of polio.