Logistical challenges and assumptions for modeling the failure of global cessation of oral poliovirus vaccine (OPV)

Figures & data

Table 1. Serotype-specific characteristics and model inputs.

Model input	Serotype 1	Serotype 2	Serotype 3	Source(s)
Last reported WPV case	Ongoing transmission in Pakistan and Afghanistan	October 1999	November 2012	[11–13]
Average paralysis-to-infection ratio for fully susceptible individuals				[10]
- WPV	1/200	1/2000	1/1000
- OPV	7.4×10^−8	6.2×10^−7	1.3×10^−6
Relative basic reproduction number (R0) for WPV or fully-reverted VDPV (relative to serotype 1)	1 (reference)	0.9	0.75	[10,14]
Relative R0 of OPV parent strain to WPV or VDPV	0.37	0.55	0.25	[10]
Average time (days) to revert from OPV to fully-reverted VDPV	620.5	408	620.5	[14]
Relative average per-dose OPV take rate (always 2>1>3, value within range depends on specific population) for recipient of trivalent OPV	0.583-0.875	1 (reference)	0.45-0.75	[7]

OPV: oral poliovirus vaccine; R₀: basic reproduction number; VDPV: vaccine-derived poliovirus; WPV: wild poliovirus.

Figure 1. Routine immunization (RI) options for successful-phased OPV cessation.

Figure 2. Routine immunization (RI) options with failure of the OPV-cessation strategy (control).

Figure 3. Routine immunization (RI) options for IPV/OPV countries with OPV restart and continued phased OPV cessation (starts at bOPV in RI as of mid-2019).

Figure 4. Routine immunization (RI) options for OPV+IPV countries with OPV restart and continued phased OPV cessation (starts at bOPV in RI as of mid-2019).

Table 2. Summary of OPV-related assumptions for prospective global-integrated economic policy models.

Model input	Value
Serotype-specific threshold number of cases since serotype-specific-OPV cessation to trigger restart of OPV for that serotype	5,000
Number of years required to fully restart OPV production while production of any licensed OPV still occurs and manufacturers maintain a stockpile of the appropriate mOPV for oSIAs	2
Number of years required to fully restart OPV production while manufacturers maintain a stockpile of the appropriate mOPV for oSIAs but have stopped production of OPV vaccine	3
Number of years required to fully restart OPV production of the first serotype (or to simultaneously restart production of more than one OPV serotype (e.g., bOPV or tOPV)) when no OPV remains available	7
Number of years required to fully restart OPV production of an additional serotype after OPV restart of another serotype already occurred	5
Minimum number of years of IPV use after cessation of the last OPV serotype (x)	10
Toggle for the availability of nOPV in the event of a restart	False
Toggle for resuming oSIAs in the event of a restart	True
Toggle for resuming pSIAs in the event of a restart	False
Toggle for continuing the global strategy of OPV cessation	Policy choice (True or False)
Type of restarted vaccine: post OPV2 cessation after detecting circulating serotype 2	tOPV or mOPV2 (+bOPV)
post OPV2 and post OPV3 cessation after detecting circulating serotype(s):
○ serotype 2	tOPV or mOPV2 (+mOPV1)
○ serotype 3	tOPV or mOPV3 (+mOPV2)
○ serotype 2 and serotype 3	tOPV
post all OPV cessation after detecting circulating serotype(s):
○ serotype 1	tOPV or mOPV1
○ serotype 2	tOPV or mOPV2
○ serotype 3	tOPV or mOPV3
○ serotype 1 and serotype 2	tOPV or mOPV1+mOPV2
○ serotype 1 and serotype 3	tOPV or bOPV or mOPV1+mOPV3
○ serotype 2 and serotype 3	tOPV or mOPV2+mOPV3
○ serotype 1 and serotype 2 and serotype 3	tOPV

bOPV: bivalent OPV; IPV: inactivated poliovirus vaccine; mOPV: monovalent OPV (mOPVx where x = 1, 2, or 3, corresponds to serotypes 1, 2, or 3, respectively); oSIAs: outbreak response SIAs; nOPV: new oral poliovirus vaccine; OPV: oral poliovirus vaccine; pSIAs: planned SIAs; R₀: basic reproduction number; SIAs: supplemental immunization activities; tOPV: trivalent OPV; VDPV: vaccine-derived poliovirus; WPV: wild poliovirus.

Figure 5. Routine immunization (RI) flowchart for blocks in the global model currently using IPV/OPV sequential schedules.

Figure 6. Routine immunization (RI) flowchart for blocks in the global model currently use OPV+IPV schedules.

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