Redefining High-Risk and Mobile Population in Pakistan Polio Eradication Program; 2024.

BACKGROUND: This study aimed to analyze the patterns and underlying reasons associated with population movement across Sindh, Pakistan. METHODS: Cross-sectional surveys were conducted in response to the detection of WPV1 in various districts in Sindh province, where genetic linkages with poliovirus isolates in Karachi had been identified. The surveys targeted union councils (UCs) contributing sewage to the environmental sample collection sites where WPV1 was detected. RESULTS: In the Karachi division a total of 1392 participants were interviewed, and outside Karachi 1471 participants were included. A significantly higher proportion of female participants were interviewed in Karachi (n = 72, 55.0%) compared to other divisions of Sindh (n = 794, 45.0%) (p < 0.001). Linguistic distribution varied significantly between regions, with Pashto speakers predominating in Karachi (n = 336, 86.4%), and Sindhi in other divisions (n = 501, 79.4%) (p < 0.001). OPV coverage exceeded 90% across all districts, and over 85% of children received RI vaccines. Travel patterns also differed significantly; participants from Karachi (n = 686, 44.2%) were less likely to report travel compared to other divisions (n = 865, 55.8%), who frequently traveled for family events, business, or employment (p < 0.001). CONCLUSIONS: It is critical to redefine high-risk populations annually based on updated mobility data, social survey analyses, and virus detection via surveillance to better identify and reach unvaccinated children in the Pakistan polio program. In addition, strategically placed PTPs along both formal and informal travel corridors based on an updated risk framework will enhance vaccination, thereby reducing the risk of virus spread.