Supplementary immunization activities (SIAs) are a key tool for polio eradication.

Regular monitoring data for SIAs, however, are often unreliable, showing high coverage levels in virtually all areas, including those with ongoing virus circulation. To address this challenge, the World Health Organization introduced digital lot quality assurance sampling (LQAS) in 2009 as an additional tool to monitor SIA quality. LQAS becomes increasingly important to address remaining gaps in SIA quality and help focus resources on high-risk areas to prevent the continued transmission of wild poliovirus.