Figure 1.
An illustration of several approaches used to define service catchment area, administrative unit (ward or subcounty), straight-line distance (10 km buffer and Thiessen polygon) and travel time (area within 60 min of a hospital). Illustration is based on 622 COVID-19 vaccination posts (https://medical.unon.org/node/169) approved in Kenya. If vaccine allocation was based on one of these catchment areas, there would be mismatches between those who attend a facility and the estimated population denominator in 20218 across methods due to lack of geolocated residential data of care seekers at a particular post. The top right corner shows the illustrated region within Samburu County, Kenya.