In 2017, only 1 out of 3 children was fully immunized in the Democratic Republic of the Congo, while 1 child out of 5 didn’t receive any vaccines (MICS Survey). In the last three years, all provinces of DRC reported cases of measles, while 60% of the 26 provinces (including Haut-Lomami and Tanganyika) reported cases of polio. Three elements are critical in understanding the high number of zero-dose and under-immunized children in DRC: low population density; lack of transportation means in rural areas; and poor population data quality. Acasus has worked with partners to provide innovative satellite-based data maps to help vaccinators build efficient and equitable vaccination strategies.