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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)

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

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 - - - - - - - -
  1. 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.