2489. Silent Polio Transmission: A Spatial Analysis
Session: Oral Abstract Session: Global Infections
Saturday, October 7, 2017: 2:45 PM
Room: 01AB

Background: As wild poliovirus is eradicated and countries switch from Oral Polio Vaccine (OPV) to Inactivated Polio Vaccine (IPV) per WHO recommendations, preventing circulation of vaccine-derived poliovirus is a top priority. However, spatial dynamics of OPV transmission are not well understood. Understanding these trends will improve resource targeting in the event of OPV reintroduction in undervaccinated communities. Mexico provides a natural environment to study OPV as it provides IPV routinely and bi-annual OPV campaigns.

Methods: Children in three villages near Orizaba, Mexico were randomized to three levels (10%, 30%, 70%) to receive OPV. We measured distance to nearest OPV shedding, and the amount of shedding close to unvaccinated individuals. We used maps to show the proximity and amount of shedding. Distance and density of shedding was analyzed separately using mixed effects logistic regression with random effects for household and time, adjusted for age, gender, area, and running water.

Results: The median distance to nearest OPV shedding was 85 meters (IQR 46, 145). The median number of shedding individuals within 200m was 3 (2, 6). Shedding and between household transmission occurred rapidly with unvaccinated individuals shedding on day one of the study (Figure 1). There was little evidence (Odds Ratio [OR] 1·04 (95% Highest Posterior Density [HPD] 0·92, 1·16)) of an association between distance (per 100 meters) from OPV shedding and odds of shedding. There was some suggestion that the number of OPV shedding within 200m may have some effect on unvaccinated shedding with OR 0·93 (HPD 0·84, 1·01) but not at 100 or 500m. Results were consistent across the three villages.

Conclusion: Household structure appears to have limited value in predicting transmission of poliovirus shedding. Use of OPV results in rapid but low levels of transmission throughout the community and this would usually go undetected. The only way to avoid this is to not use OPV or to have strong controls such as quarantine, or strict hygiene protocols. After withdrawal of OPV worldwide the decision to reintroduce due to an outbreak should not be taken lightly as it appears a small amount of OPV is needed to result in transmission.

Figure 1: Contour Plot: Shedding Over Time

Christopher Jarvis, MSc1, Jonathan Altamirano, MS2, Clea Sarnquist, DrPh, MPH2, Lourdes Garcia-Garcia, MD3, Leticia Ferreyra Reyes, MD3, Rogelio Montero-Campos, MS3, Luis Pablo Cruz-Hervert, MSc3, Marisa Holubar, MD, MS4, Aisha Talib, MPP2, Natasha Purington, MS2, Meira Halpern, PhD2, Rasika Behl, MPH2, Elizabeth Ferreira, MD3, Guadalupe Delgado, MPH3, Sergio Canizales Quintero, BA3, Manisha Desai, PhD2, John Edmunds, PhD1 and Yvonne Maldonado, MD, FIDSA, FPIDS2, (1)Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom, (2)Pediatrics, Stanford University School of Medicine, Stanford, CA, (3)Instituto Nacional de Salud P├║blica, Cuernavaca, Mexico, (4)Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA


C. Jarvis, None

J. Altamirano, None

C. Sarnquist, None

L. Garcia-Garcia, None

L. Ferreyra Reyes, None

R. Montero-Campos, None

L. P. Cruz-Hervert, None

M. Holubar, None

A. Talib, None

N. Purington, None

M. Halpern, None

R. Behl, None

E. Ferreira, None

G. Delgado, None

S. Canizales Quintero, None

M. Desai, None

J. Edmunds, None

Y. Maldonado, None

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