The polio endgame and silent circulation: some related research

2 | Domains of work for polio endgame Risk assessment and SIA planning: prevention and awareness OPV cessation: prevention of VDPV through targeted pre-switch vaccination AFP surveillance: robust identification of risk of surveillance failure/gaps Elimination probability: epidemiology and modeling informing the probability of elimination Environmental surveillance: a surveillance mode worth expanding in the endgame

3 | Risk assessment: prevention of circulation through motivating SIAs Risk assessment task team (RATT): semiannual country risk assessment supporting SIA planning and program action (BMGF, CDC, IDM, UNICEF, WHO/Imperial) Characterize susceptibility and exposure Categorize risk Provide SIA recommendations SIA's vs. Underimmunized targets Scaling prevention efforts to vaccination targets in AFRO/EMRO/SEARO (not RATT)

4 | OPV cessation: emergence risk reduction through pre-switch SIAs Cessation of OPV2 is slated for April 2016: prevention of cVDPV2 emergence by vaccination is a critical GPEI strategy. Motivate strategy Identify areas of risk Propose SIAs for the right scale of vaccination efforts by country

5 | Identifying gaps in the AFP surveillance system AFP surveillance failure is a major risk for undetected circulation. Vigilance of regional surveillance risks was and is a key GPEI strategy. RATT surveillance assessment: improving rigor and stability of noisy indicators Identify poor performing countries and sub- national areas for remediation Limited by the lack of identifiability of incidence rate and detection probability Undetected circulation very consequential: False security of fadeout/elimination: “foot off the gas” Reversion Geographic scope of (OPV) SIA response, particularly in the post-OPV era

6 | Modeling silent transmission during low periods How long after a case before we should believe polio is gone? If it isn’t gone, when should we expect the next case? Approach with detailed spatial and hybrid statistical- dynamical models Tailor prediction to each situation Nigeria today (June 26, 2015): -WPV1 probably eliminated from Nigeria -WPV3 very likely eradicated -cVDPV2 from established lineages likely persists March 31, 2015 Environmental Positive arXiv: Under review McCarthy et al In prep

7 | Environmental surveillance: a partial solution for silent circulation ES is expanding surveillance instrument increasingly critical in endgame…and worth further expansion. ES targets infections not paralytic cases, albeit in a limited catchment Case to infection changes in the endgame – IPV reduces case to infection – Sabin  fully reverted VDPV plausibly spans case to infection ratios from ~1 in 1M to wild-like – OPV2 cessation and VDPV2 risk: type 2 has lowest case rate ES questions: Where should ES be deployed? What sensitivity is expected? How can ES be made more scalable? Can ES be made more quantitative?