Modeling undetected live poliovirus circulation after apparent interruption of transmission: implications for surveillance and vaccination

Table 2 Expected detected-event free period (DEFP) required for 95% and 99% confidence about no circulation (CNCx%) and time of undetected circulation between the last paralytic case and die-out (TUCx%) by serotype (based on 1,000 iterations) assuming perfect surveillance (top) and imperfect surveillance (bottom)

Virus	WPV1 (PIR = 1/200)				cVDPV2 (PIR = 1/ 2000)				WPV3 (PIR = 1/1000)
Metric	CNCx%		TUCx%		CNCx%		TUCx%		CNCx%		TUCx%
x%	95%	99%	95%	99%	95%	99%	95%	99%	95%	99%	95%	99%
Population	DEFP values assuming perfect AFP surveillance without environmental surveillance
Northern India	0.67	0.83	0.65	0.74	1.58	2.00	1.39	1.96	0.83	0.92	0.77	0.86
Northwest Nigeria
- current path	1.00	1.25	0.98	1.23	2.08	2.67	1.95	2.28	2.83	3.58	2.61	3.53
- increased tOPV	1.08	1.25	1.01	1.24	1.50	1.67	1.36	1.58	2.92	3.58	2.65	3.53
Tajikistan	0.42	0.50	0.35	0.38	-	-	-	-	-	-	-	-
Israel	1.25	1.42	1.19	1.36	-	-	-	-	-	-	-	-
Population	DEFP values assuming AFP surveillance with quality based on Table 1 (including environmental surveillance in Israel)
Northern India	0.67	0.83	0.66	0.77	1.75	2.25	1.51	2.19	0.83	0.92	0.80	0.87
Northwest Nigeria
- current path	1.25	1.50	1.22	1.48	2.33	2.92	2.16	2.53	3.75	4.33	3.62	4.27
- increased tOPV	1.25	1.58	1.22	1.54	1.58	1.75	1.47	1.66	3.58	4.17	3.45	4.17
Tajikistan	0.42	0.50	0.36	0.38	-	-	-	-	-	-	-	-
Israel	0.92	1.17	0.76	1.15	-	-	-	-	-	-	-	-

Abbreviations: CNCx%, DEFP at which the confidence about no circulation exceeds x%; cVDPV, circulating vaccine-derived poliovirus; DEFP, detected-event-free period; OPV, oral poliovirus vaccine; PIR, paralysis-to-infection ratio; tOPV, trivalent OPV; TUCx%, time at which the probability of undetected WPV circulation after the true last case becomes exceeds x%; WPV, wild poliovirus.

ISSN: 1471-2334