Most Health Information Systems (HIS) in developing countries are fragmented and characterized by multiple overlapping and/or duplicate sub-HIS. The fragmentation of HIS is further identified by many researchers as the biggest problem shaping their use and utility. A shared vision to solve the issues of fragmentation is to move towards integrated HIS. Integrated HIS has the potential to improve decision-making and the overall health management. Focusing on the information systems used for the management of Tanzania’s vaccine supply chain, this thesis critically assesses the potential benefits and challenges of integrating various information systems with the national Health Management Information System (HMIS). This is done by analyzing how and why Tanzania’s HIS is fragmented, what challenges this fragmentation leads to, and identifying the possibilities and challenges for integration. The research is based on a qualitative case study conducted at different levels of the health system in and around Dar es Salaam, Tanzania, in two separate field trips. Findings indicate that Tanzania’s fragmented HIS leads to multiple challenges that may negatively affect the overall health services. Different formats and inflexible systems, differences in how data is defined and understood, as well as different interests and procedures for the various actors involved, challenges the idea of integrated HIS. Integration can solve some of the existing challenges of fragmentation, but it will also require intricate negotiations and alignment of interests between the myriad of actors involved. Therefore, one should consider if the potential benefits of integration is worth the effort. Drawing on existing theory on socio-technical information systems, Information Infrastructures, fragmentation and integration, the overall objective of this thesis is to contribute with richer insight into the benefits and challenges of moving from fragmented to integrated HIS in developing countries. It also contributes by applying an integrative framework based on Carlile’s (2004) work to analyze fragmentation and discuss how to address integration at the technical, data and organizational level of HIS.