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Fig. 5 | BMC Medicine

Fig. 5

From: The risk of type 2 oral polio vaccine use in post-cessation outbreak response

Fig. 5

Dependence of the position of the 50% separatrix line on immunity levels in the cohort of children born before cessation: 100% immunity (dashed lines) vs. immunity induced by three rounds of OPV at 80% coverage, 50% take (solid lines). All lines at constant g = 0.5, N IPV = 1, c = 1, λ = 60 days. The cyan, red, gray, and black lines, respectively, indicate R 0f values of 3, 2, 1.5, and 1.2. The final R 0 is observed to have the dominant effect. The thin black dashed box indicates migration rates that are preferred by a calibration to a single traveling WPV1 outbreak in the region, in 2008. The effect of increasing immunity in the older cohort is largest at higher R 0, as higher R 0 facilitates more transmission through partially immune older children. However, the additional protection is somewhat modest (considering the extreme assumption of perfect immunity in all children born pre-cessation), indicating that the cohort of children born post-cessation rapidly becomes a dominant contributor to OPV2 transmission in this model

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