AFP and infection: If the risk of infection was greater among younger children, the estimated median monthly sensitivity of AFP surveillance almost doubled to 13.8% (5th-95th percentiles 9.1-19.7%, mean 14.0%) for a design prevalence of 10-5, and 1.5% (5th-95th percentiles 1.0-2.2%, mean 1.5%) for a design prevalence of 10-6 respectively.