ORAL POLIO VACCINE STATUS AND OCCURENCE OF WILD POLIO VIRUS AMONG REPORTED ACUTE FLACCID PARALYZED CHILDREN IN NIGERIA

Abstract

Nigeria remains one out of the three countries in the world yet to interrupt endemic Poliomyelitis. The disease thus continues to thrive in Nigeria, Afghanistan and Pakistan. Four doses of OPV have been used in the Polio Eradication Initiative Programme in Nigeria. However, a single dose of Oral Polio Vaccine has been known to produce immunity to approximately 50% of recipients and three doses to 95%. Thus multiple Immunization Campaigns have been carried out and yet there is failure to eradicate Poliomyelitis. This failure to eradicate the disease globally raises the question of the effectiveness of the continuing use of 4 doses of OPV in the prevention programme in endemic Countries. Understanding the association between the Oral Polio vaccine Status and Wild Poliovirus cases among AFP cases could help provide details for policy direction on the number of OPV to be given during Campaigns. This study was therefore conducted to determine the optimum OPV dose for prevention of Wild Poliovirus in Nigeria and its Clinical Effectiveness under field conditions in the actual community. Secondary data analysis from 2009 to 2012 of the National AFP Surveillance System from the 36 states and FCT in Nigeria was done. Descriptive statistics was used to describe AFP occurrence. OR and ROC curve was used to determine the clinical effectiveness of OPV and logistic regression used to identify predictors of the disease. A total of 24848 cases of AFP were analyzed. About half were between 12-35 months of age with 57% males. Northern states had the highest occurrence of AFP cases reported (29%).A majority (70.7%) had received over 3 doses. Efficacy of OPV was found to be maximized in children who had received 4 doses (92%) followed by 80% in those with 3 doses and 57% in those with 2 doses.OPV sensitivity and specificity was maximum at a cut-off point of 4 doses producing the best efficacy on the ROC curve. It is therefore recommended that 4 doses of OPV should be continued in the National Polio Eradication Programme.