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Following the 1988 World Health Assembly resolution to eradicate polio, the number of polio-endemic countries decreased from 125 in 1988 to 6 in 2003 (Afghanistan, Egypt, India, Niger, Nigeria and Pakistan). The Global Polio Eradication Initiative faced a serious challenge in 2003-2005 with a resurgence of polio cases across sub-Saharan Africa, originating from Nigeria. Following the suspension of supplementary immunization activities (SIAs) in some northern states, (1) Nigeria experienced increased wild poliovirus (WPV) transmission throughout the country. From 2003 to 2005, WPV originating from Nigeria spread into 18 countries that had been polio-free for 1 or more years, including 3 countries outside Africa (Indonesia, Saudi Arabia and Yemen). (2-5) Virus transmission was re-established and continues in 6 of these countries (Burkina Faso, Central African Republic, Chad, Cote d'Ivoire, Mali and Sudan). This report summarizes the polio eradication activities in Nigeria from January 2004 to July 2005 and the actions being taken towards interrupting WPV transmission in Nigeria as soon as possible.
In 2003, a national immunization coverage survey in Nigeria estimated that 31% of children aged <12 months nationwide had received 3 doses of diphtheria-tetanus-pertussis vaccine, (DTP3), ranging from 6% in the north-west administrative zone to 68% in the south-west administrative zone. DTP3 coverage is used as a proxy for routine infant coverage with 3 doses of oral poliovirus vaccine (OPV3) by 12 months of age.
Supplementary immunization activities
From 1999 to 2002, national immunization days (NIDs)(6) were conducted annually, targeting children aged <5 years. In 2003, a global funding shortfall restricted SIAs in Nigeria to 9 rounds of subnational immunization days (SNIDs), (7) targeting various endemic northern states. The state governments of Kaduna, Kano, Zamfara and, to a limited extent, that of Niger suspended several SIA rounds during 2003-2004 because of unfounded rumours about the safety of OPV. In Kano, the most populous of these states (estimated 2004 population of 7.7 million), state authorities suspended all SIAs from April 2003 to July 2004, which resulted in decreased acceptance of OPV in all northern Nigerian states.
Nigeria conducted 5 NID rounds in 2004, targeting all 37 states (36 states plus the Federal Capital Territory). Kano did not participate in the January and March rounds and Zamfara missed the January round. With the resumption of activities in Kano, SNIDs were conducted in July and September 2004 in 8 endemic north-western Nigerian states. (8) Five NID rounds and 1 SNID round were planned for 2005; the number of children reached has steadily increased with each SIA round during 2004-2005. Independent monitoring shows, at the national level, that the estimated proportion of children not vaccinated is decreasing (from
17% in the October 2004 round to 7% in the May 2005 round), as is the number of households not visited (from 7% to 3%, respectively).
Certain population groups living in riverine areas, including nomadic cattle herders, fishermen and hard-to-reach settled communities--with an estimated population of more than 10 million--have been poorly reached by both routine immunization services and SIAs. As determined from independent monitoring of SIAs and investigation of acute flaccid paralysis (AFP) and polio cases, children in these high-risk groups contribute substantially to low overall childhood population immunity. Specialized teams are now carrying out outreach activities to provide these groups with OPV and other vaccines. Over 22 000 children from these communities, who had never previously received OPV, were immunized during SIAs in 2005.
The OPV vaccination status (the total number of doses received through routine and supplementary immunization) of children aged 6-59 months with non-polio AFP is used as a proxy for the immunity level of the age group targeted by SIAs (children aged <5 years). In the 13 Nigerian states where polio is endemic, (9) the proportion of non-polio AFP cases who had received >3 doses of OPV increased from 15% for cases with onset in the first half of 2004 (range: 1.6-51%) to 19% for cases with onset in the first half of 2005 (range: 0-60%). In comparison, in the 18 states without confirmed polio cases in 2005, (10) this proportion was 66% (range: 27-85%) in the first half of 2004 compared with 71% (range: 40-96%) in the first half of 2005.
Acute flaccid paralysis surveillance
Surveillance for AFP is conducted at 4993 reporting sites in Nigeria's 774 local government areas (LGAs). AFP surveillance quality is evaluated using 2 key performance indicators: (i) the annual AFP reporting rate (target: non-polio AFP rate of [greater than or equal to] cases per 100 000 children aged <15 years) (11) and (ii) the completeness of stool specimen collection (target: two adequate specimens (12) from …