Quantifying movement patterns and vaccination status of high risk mobile populations in Pakistan and Afghanistan to inform poliovirus risk and vaccination strategy

Abstract

Background: Stopping serotype 1 wild poliovirus transmission in Pakistan and Afghanistan requires ensuring all children <5 years of age are repeatedly vaccinated, including the large proportion living in mobile groups. Vaccinating children living in high-risk mobile populations (HRMPs) remains a priority for the polio programme.

Methods: In 2017-2018, group-level censuses were conducted in 43 districts of Pakistan, gathering information for all HRMP children <5 years of age residing in settlements. Demographic and mobility information was collected, including HRMP type, ethnicity, language, mode of transportation and movement patterns. Vaccination status was recorded for the most recent polio campaign. Proportion of HRMP children by demographic factors and mode of transportation was determined and the magnitude of movement was quantified based on the origin, previous and next locations. Magnitude of cross-border movement with Afghanistan was evaluated, as was primary crossing point. Vaccination status was evaluated for each district by demographic and mode of transportation information.

Results: In total, 188,130 HRMP children <5 years of age were assessed. The predominant HRMP type, ethnic group, language and mode of transport was Afghan refugees (27%), Pashtun (69%), Pashto (69%) and bus (52%). Overall, 84% of children originated outside of their current district, including 29% from Afghanistan. Previous and next locations, were reported outside of current location by 34% and 77% of children. Afghanistan was previous and next location for 5% and 11% of children, with 5.5% and 3% of children crossing the Afghanistan border in the past 6-months and next 3-months. Primary crossing route was Torkham (79%). Overall vaccination coverage was 98% (IQR: 96%-99%) and consistently >90% across HRMP type, ethnic group, language and mobility means.

Conclusion: Large numbers of HRMPs were found across Pakistan, with substantial links throughout the country and with Afghanistan. While vaccination coverage of HRMPs was high, ensuring these populations are consistently vaccinated remains a priority.

Keywords: Mobile populations; Movement patterns; Pakistan and Afghanistan; Poliovirus risk; Vaccination.