Designing a National Rapid Vaccine Coverage Survey in low-resource settings: Experiences from the Democratic Republic of the Congo 2018-2023.

In the Democratic Republic of the Congo (DRC), estimating vaccine coverage (VC) has traditionally relied on large-scale surveys such as the Demographic and Health Surveys (DHS) and the Multiple Indicator Cluster Surveys (MICS). However, these surveys are infrequent, costly, and lack the granularity needed for decision-making at the health district or zone (HZ) level. This paper describes the development by the Kinshasa School of Public Health (KSPH), and technical partners of a Vaccine Coverage Survey (KSPH VCS), adapted from the World Health Organization (WHO) guidelines, which aims to provides timely, cost-effective, and representative estimates of VC at the HZ level. The KSPH VCS adopted a cross-sectional design and a multi-stage sampling approach to sample households at the HZ level. It uses Health Area as cluster in spite of Enumeration Area, and extends the eligibility age range from 12 -23 months to 6-23 months. The sample size for each HZ was calculated using vaccine coverage provided in MICS-2018. It integrates assessments of barriers and enablers to vaccination. Since 2023, it has included malaria indicators. Since its inception in 2018, it has expanded nationwide, covering all 26 provinces of the DRC by 2022. Findings from the KSPH VCS provides estimates at the HZ level that could be combined to provincial and national estimates. Results have been instrumental in evaluating national immunization strategies, including the Mashako Plan and informing Presidential Forums on immunization. They have informed resource allocation, operational planning, and policy decisions at both national and provincial levels as they provided granularity needed for operational decision-making at the HZ level. Its results have also contributed to global immunization estimates, including the WHO/UNICEF Estimates of National Immunization Coverage (WUENIC). The KSPH VCS demonstrates the feasibility of a locally led, cost-effective, and adaptable VC survey in a low-resource setting. Its success highlights the potential for similar methodologies to be implemented in other low- and middle-income countries seeking to improve immunization monitoring and health system performance.