Abstract
A priority of the Global Polio Eradication Initiative (GPEI) 2013–2018 strategic plan is to evaluate the potential impact on polio eradication resulting from expanding one or more Supplementary Immunization Activities (SIAs) to children beyond age five-years in polio endemic countries. It has been hypothesized that such expanded age group (EAG) campaigns could accelerate polio eradication by eliminating immunity gaps in older children that may have resulted from past periods of low vaccination coverage. Using an individual-based mathematical model, we quantified the impact of EAG campaigns in terms of probability of elimination, reduction in polio transmission and age stratified immunity levels. The model was specifically calibrated to seroprevalence data from a polio-endemic region: Zaria, Nigeria. We compared the impact of EAG campaigns, which depend only on age, to more targeted interventions which focus on reaching missed populations. We found that EAG campaigns would not significantly improve prospects for polio eradication; the probability of elimination increased by 8% (from 24% at baseline to 32%) when expanding three annual SIAs to 5–14 year old children and by 18% when expanding all six annual SIAs. In contrast, expanding only two of the annual SIAs to target hard-to-reach populations at modest vaccination coverage—representing less than one tenth of additional vaccinations required for the six SIA EAG scenario—increased the probability of elimination by 55%. Implementation of EAG campaigns in polio endemic regions would not improve prospects for eradication. In endemic areas, vaccination campaigns which do not target missed populations will not benefit polio eradication efforts.
Highlights
In May 2012, the World Health Assembly declared the eradication of polio a ‘‘programmatic emergency for global public health’’ and called for a comprehensivePLOS ONE | DOI:10.1371/journal.pone.0113538 December 1, 2014Polio Expanded Age Group Campaigns: Quantifying Impact polio endgame strategy [1]
To quantify the effect of expanded age group (EAG) campaign implementation, we took a posterior distribution sample from the results of our calibration procedure, and compared the overall type-1 wild poliovirus (WPV1) prevalence and age stratified mucosal immunity when the targeted age group was extended to children less than 15 years of age
Even under the most optimistic assumptions that EAG campaigns would be employed in 6 Supplementary Immunization Activities (SIAs) per year and result in a 20% relative increase in overall coverage levels, the probability of elimination increased by 16%
Summary
In May 2012, the World Health Assembly declared the eradication of polio a ‘‘programmatic emergency for global public health’’ and called for a comprehensivePLOS ONE | DOI:10.1371/journal.pone.0113538 December 1, 2014Polio Expanded Age Group Campaigns: Quantifying Impact polio endgame strategy [1]. In May 2012, the World Health Assembly declared the eradication of polio a ‘‘programmatic emergency for global public health’’ and called for a comprehensive. Major progress has been made since the founding of the Global Polio Eradication Initiative (GPEI) Program in 1988 [2]. Polio is endemic in only three countries as of 2014, and case counts are reaching historic lows. For the first time ever, the world is on the verge of eradicating wild poliovirus. Achievement of this goal will benefit future generations and allow the more than one billion dollar annual budget for GPEI to be directed towards other health and development goals
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