Vertical immunization information system or integrated one?

This is a great question, and the answer is, as always, it depends.

I suggest you read a recent publication I co-authored called Critical Success Factors for Deploying Digital LMIS, which addresses the LMIS aspects of this question. I know some countries (like Tanzania) have opted to integrate service delivery (HMIS) and supply chain (LMIS) into a single information platform called the Vaccine Information Management System (VIMS). However, VIMS was built as a module with the integrated eLMIS for all products using the OpenLMIS platform, which has been extended to support all immunization program data. Others, such as Ethiopia, have integrated vaccine supply chain information data into an integrated LMIS, while letting the HMIS technology solutions provide for other EPI program data requirements.

My personal suggestion is that supply chains should be supported with software solutions that are specifically designed to support the workflows and business processes of a supply chain; see  Information Systems for Supply Chain Management: The case for connecting separate and interoperable technology applications for Logistics Management Information System and Health Information Management Systems dataInformation Systems for Supply Chain Management: The case for connecting separate and interoperable technology applications for Logistics Management Information System and Health Information Management Systems data.

I have seen many different approaches. It really depends on the country, how EPI is organized and who has the responsibility to monitor service delivery and the supply chain. In some countries, the EPI is reposnible for both, in others the EPI for one or the other, or none; in some countries the supply chain is monitored by a LMIS that includes not only vaccines but other medications, in others not; same with HMIS, in some countries this is the only system to monitor doses administered, while in other countries there are parallel systems EPI and HMIS. 

The most important aspect, I would say, is to ensure that whatever electronic info system is used meets all the needs (managerial and for monitoring) and functional standards requiered by all persons involved, at different levels. In a few countries (that I have seen), they have managed to integrate both systems and make them inteact with each other. For example, in teh city of Bogota, there is an electronic registry that crosses info with the supplies used and wastage. 

I would recommend reading the Optimize Manual on the topic: "Planning an Information Systems Project: A Toolkit for Public Health Managers". This toolkit can help public health managers plan for the implementation of information and communications technology in health information systems. It draws on lessons learned by project Optimize, a five-year collaboration between the World Health Organization and PATH, to help optimize the vaccine supply chain. Author(s): Grevendonk J, Taliesin B, Brigden D. Corporate author(s): PATH, World Health Organization. Publication date: July 2013. Available at:  https://www.path.org/publications/detail.php?i=2343 

An interesting question. In the US, Immunization Immunization Systems (IIS) are state-run systems not a single, large Federal system for the whole country. Some large municipalities (like NYC) and US territories (like Puerto Rico) have their own as well.

By and large, IIS are single-purpose public health registries that serve only immunization program needs. But there are some exceptions. Is the State of Rhoad Island, for instance, we support a comprehensive child health system called KIDSNET (http://www.health.ri.gov/programs/kidsnet/index.php) which covers many child health programs and integrates the data together for both the clinical community and public health surveillance. In NYC we created a Master Person Index to help the IIS (called the Citywide Immunization Registry, or CIR) and Lead Poisoning Prevention information system (called LeadQuest) interoperate and exchange data without becoming fully integrated since they are controlled by different parts of the agency. Other examples exist as well.