After progress towards polio eradication during 1996 to 2002, Nigeria suffered a resurgence of wild poliovirus (WPV) transmission due to the suspension of vaccination campaigns in the autumn of 2003 in a number of states in the north, particularly Kano. This resurgence resulted in the reintroduction of WPV into previously polio-free Nigerian states and the exportation of WPV to eight polio-free countries in west and central Africa (Benin, Burkina Faso, Cameroon, Central African Republic, Chad, Côte d'Ivoire, Ghana and Togo).

The increased intensity of WPV transmission in states with endemic poliomyelitis in northern Nigeria in 2003 occurred despite an increased number of targeted supplementary immunization activities (SIAs). Of the 13 states with endemic disease, seven were involved in four or more subnational immunization day (SNID) rounds in 2003; all 13 states have continued to confirm WPV. Continued WPV transmission with expansion of genetic diversity, the occurrence of polio in older children and oral poliovirus vaccine data from non-polio acute flaccid paralysis cases demonstrate the failure to reach a significant proportion of children during the vaccination campaigns.

False rumours about oral poliovirus vaccine safety adversely affected SNIDs, with the greatest impact in Kano, where 25% of all Nigerian WPV cases occurred in 2003. Citing vaccine safety concerns, state authorities in Kano (which last conducted a SNID in April 2003) decided in August 2003 to suspend all SIAs. Statewide suspension of SIAs at different times during 2003 and 2004 also occurred in Kaduna, Zamfara and, to a limited extent, in Niger state. In the context of these rumours, public health managers and frontline health workers have found it increasingly difficult to improve micro-planning, training and implementation of SIAs.

Source: WHO Weekly Epidemiological Report, Vol 79, No 17, 2004. (Editorial note)

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