RESUMO
OBJECTIVES: To demonstrate the immunity status of children with non-polio acute flaccid paralysis (NP AFP) reported through the AFP surveillance system in the South-South region of Nigeria. STUDY DESIGN: A retrospective study was conducted using AFP surveillance data collected routinely between January 2011 and December 2014 by the Disease Surveillance Department of the regional health service and the World Health Organization (WHO)-accredited regional reference polio laboratory. All cases of AFP reported to the Disease Surveillance Network from all six zones during this period were included in the study. METHODS: In total, 5111 cases of AFP in children aged ≤15 years were reported between 2011 and 2014. These cases were investigated and verified by WHO surveillance officers using a standard questionnaire, which captured the number of doses of oral polio vaccine (OPV) received by the child. Two stool samples were collected for each case, 24-48 h apart, within 14 days of the onset of paralysis, and transported to the national polio laboratory under reverse cold chain storage. Data retrieved were stored in an AFP database hosted by the WHO server. EPIINFO software was used to query the database and extract the information required for analysis in this study. RESULTS: The percentage of children who had received at least three doses of OPV (which serves as a threshold to measure immunity status) decreased from 87% in 2011 to 82% in 2014. The percentage of children who had not received any doses of OPV decreased from 2% in 2011 to 1% in 2014. Forty-eight percent of the children who had not received any doses of OPV were aged <1 year. CONCLUSION: Given the decrease in OPV immunity status, the region risks re-introduction of poliovirus. Swift steps should be taken to improve the immunization coverage, which would boost immunity status in Nigeria.
