Since 2014, PATH has been working with the Tanzania Ministry of Health (MOH) under the immunization and vaccine development (IVD) program to implement the better immunization data (BID) initiative in Tanzania. The BID initiative is grounded in the belief that better data and better decisions will lead to better health outcomes. The vision at BID initiative is to support countries to enhance immunization and overall health service delivery through improved data collection, quality, and use. In partnership with the MOH through the IVD Program, the BID initiative identified several critical data-related challenges in issues of data quality, limited data use capacity, inaccurate or uncertain target populations, poor visibility into vaccine supplies, and difficulty identifying children who defaulted on immunization schedules. As part of resolving these challenges, the BID initiative, in consultation with the MOH, introduced a holistic package of interventions in Tanzania. This included information system products, evidence-based practices, and capacity-building to empower health workers at all health system levels toward data-driven action. The key outcomes of this work were:An electronic immunization registry with supply chain information integrated into the vaccine information management system.Barcodes on child health cards and vaccine supplies for unique identification of children and vaccine management, respectively.A change management package, including peer support networks, targeted supportive supervision, and mentorship.From 2015 through 2020, the designed interventions were deployed in 3,748 health facilities in 15 regions of Tanzania: Arusha, Dar es Salaam, Dodoma, Geita, Katavi, Kigoma, Kilimanjaro, Lindi, Morogoro, Mtwara, Mwanza, Njombe, Rukwa, Ruvuma, and Tanga.