Epidemiology and control of polioviruses in Nigeria
Author(s)
Jenkins, Helen
Type
Thesis
Abstract
Although the World Health Assembly resolved to eradicate wild poliovirus (WPV) by 2000, four countries have yet to interrupt transmission of WPVs. As of 2009, Nigeria has reported the largest burden of poliovirus of any single country for 5 of the last 6 years and been responsible for the largest outbreak of circulating vaccine-derived poliovirus (cVDPV) to date. With surveillance data on 36,410 acute flaccid paralysis cases from 2001-2009 in Nigeria, I use case-control methods to estimate vaccine efficacies of trivalent and monovalent oral polio vaccines (tOPV and mOPVs, respectively) against paralysis by all types of poliovirus circulating in Nigeria (serotypes 1 and 3 WPV and serotype 2 cVDPV (cCDPV2)). I show that mOPVs are substantially more efficacious than tOPV against serotype 1 and 3 and that tOPV is substantially more effective against cVDPV2 than against serotypes 1 and 3 WPVs. i use these results to investigate temporal and spatial variation in vaccine-induced immunity. I also estimate vaccine coverage and thus demonstrate that polioviruses persist in northern Nigeria as a result of low vaccine coverage and not due to any geographical variation in vacine efficacy. I show that the clinical characteristics and attack rate of cVDPV2 are as would be expected of a WPV and therefore similar control methods should be used. Using a proportional hazards model, I demonstrate that the risk of reporting cVDPV2 is strongly localised and cVDPV2 can be controlled with well targeted use of tOPV whilst maintaining control of WPVs with mOPVs. Finally I use negative binomial regression to estimate the predictors of incidence by geographical state in Nigeria. I conclude that the prospects for elimination of all polioviruses in Nigeria are very good with targeted use of vaccines of the appropriate serotype and provided vaccine coverage can be improved in high incidence areas.
Date Issued
2010
Date Awarded
2010-12
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Grassly, Nick
Donnelly, Christl
Sponsor
Medical Research Council
Creator
Jenkins, Helen
Publisher Department
Infectious Disease Epidemiology
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)