Modeling the prevalence of immunodeficiency-associated long-term vaccine-derived poliovirus excretors and the potential benefits of antiviral drugs

Table 2 Assumed distribution of wild poliovirus serotype 1 R₀ values for the different income level and current polio vaccine use strata, as used in the global model, and assumed simplified burn-in period [23]^a

Income level (as of 2013)	Polio vaccine(s) used (as of 2013)	Population size in billions (as of 2013)	Years until OPV use starts^b	Year until IPV-only or IPV/OPV starts^b	Number of assigned blocks	Number of blocks assigned to each R₀ (for WPV1)
Income level (as of 2013)	Polio vaccine(s) used (as of 2013)	Population size in billions (as of 2013)	Years until OPV use starts^b	Year until IPV-only or IPV/OPV starts^b	Number of assigned blocks	4	5	6	7	8	9	10	11	12	13
Low	OPV-only	0.86	33	N/A	8	0	0	0	0	0	1	3	2	1	1
Lower middle	OPV-only	2.48	33	N/A	25	0	0	1	4	5	2	0	10	1	2
Upper middle	OPV-only	1.87	20	N/A	19	0	0	1	16	2	0	0	0	0	0
Upper middle	IPV/OPV	0.50	20	58	7	0		2	3	2	0	0	0	0	0
High	IPV/OPV	0.23	10	50	2	0	0	0	2	0	0	0	0	0	0
High	IPV-only	1.02	10	50	10^c	2	7.7	0.3	0	0	0	0	0	0	0

^aDoes not include countries with unspecified income level totaling approximately 23 million people and two high-income countries that still use OPV-only totaling approximately 34 million people (all as of 2013); Assigns 67 million people in IPV/OPV-using lower middle-income countries to IPV/OPV-using upper middle-income blocks, 74 million people in IPV-only using upper middle-income countries to IPV-only-using high-income blocks, and 23 million people in OPV-only-using high-income countries to OPV-using lower or upper middle-income blocks
^bYears relative to beginning of burn-in period 65 years ago (i.e., 1950)
^cIncludes some blocks with subpopulations assigned to different R₀ values