Accurate estimates of un- and under-immunized populations at various administrative units are key for an effective planning and delivery of various human-rights-based services within a country, especially immunization services such as routine vaccination and campaigns, birth registration services, and humanitarian responses. However, due to outdated censuses, inaccessible areas (due to conflicts, extreme weather conditions, etc) movement of populations and lack of capacity, this data is often out of date, incomplete or unavailable in many countries. To bridge this gap, the “Reach the Unreached” initiative aimed to develop these essential datasets, and present them in current, reliable and actionable digital maps.  

This work initially focused on six countries in West and Central Africa (Cameroon, Chad, Côte d’Ivoire, Guinea, Mali and Nigeria), but it only produced datasets for five countries, Nigeria was excluded due to having different priorities within the Nigeria Government. WorldPop at the University of Southampton produced geolocated and disaggregated (by age and sex) estimates of population, as well as estimates of zero-dose and under-immunized children (using DPT-1 and DPT-3 data), foundational to the delivery of vaccination and birth registration services to hard-to-reach communities.

The project had three phases: 

• Country consultations to engage and agree with in-country stakeholders on the methodology and best available source of input datasets, so that the final data products meet national expectations and has the potential for maximum uptake. 
• Production of the core data layers (population-, vaccination coverage- and zero dose estimates). 
• Data dissemination and capacity building to ensure sustainability of data use. 

The technical work was followed by writing up of the methodologies and results in country reports and disseminating these through on-line further engagements with in-country stakeholders.