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%) in Pakistan and Afghanistan assuming perfect and imperfect surveillance (based on 1,000 iterations)
| Virus | WPV1 (PIR = 1/200) | cVDPV2 (PIR = 1/2000) | WPV3 (PIR = 1/1000) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| POE | 100% | 49% | 99% | |||||||||
| Metric | CNCx% | TUCx% | CNCx% | TUCx% | CNCx% | TUCx% | ||||||
| x% | 95% | 99% | 95% | 99% | 95% | 99% | 95% | 99% | 95% | 99% | 95% | 99% |
| DEFP values assuming perfect AFP surveillance without ES | ||||||||||||
| current path | - | - | - | - | 2.58 | 3.00 | 2.23 | 2.53 | 2.25 | 2.83 | 1.84 | 2.40 |
| increased relative SIA coverage 0.20 | 1.42 | 1.58 | 1.35 | 1.55 | - | - | - | - | - | - | - | - |
| increased relative SIA coverage 0.15 | 1.48 | 2.08 | 1.51 | 1.90 | - | - | - | - | - | - | - | - |
| DEFP values assuming worst performing surveillance (AFP with ES) | ||||||||||||
| current path | - | - | - | - | 3.75 | 3.83 | 3.19 | 3.34 | 4.67 | 6.42 | 3.39 | 5.70 |
| increased relative SIA coverage 0.20 | 2.33 | 2.42 | 2.28 | 2.40 | - | - | - | - | - | - | - | - |
| increased relative SIA coverage 0.15 | 3.25 | 3.67 | 3.14 | 3.55 | - | - | - | - | - | - | - | - |
| DEFP values assuming best performing surveillance (AFP with ES) | ||||||||||||
| current path | - | - | - | - | 0.25 | 0.33 | 0.22 | 0.25 | 1.17 | 1.50 | 0.70 | 1.36 |
| increased relative SIA coverage 0.20 | 0.67 | 0.92 | 0.59 | 0.87 | - | - | - | - | - | - | - | - |
| increased relative SIA coverage 0.15 | 0.75 | 0.92 | 0.62 | 0.82 | - | - | - | - | - | - | - | - |
Abbreviations: AFP, acute flaccid paralysis; CNCx%, DEFP at which the confidence about no circulation exceeds x%; cVDPV, circulating vaccine-derived poliovirus; DEFP, detected-event-free period; ES, environmental surveillance; PIR, paralysis-to-infection ratio; POE, probability of eradication; TUCx%, time at which the probability of undetected WPV circulation after the true last case becomes exceeds x%; WPV, wild poliovirus.