Background: The dominant theoretical basis of our public health practice originates from a positivist or reductionist paradigm. It fails to take into account the complexity emerging out of public health's multiple influences originating from biological and social worlds. A deeper understanding of the interaction of elements that characterize the implementation of public health functions will enhance our ability to generate evidence and learn further. Objective: The "interactive governance theory" by Jan Kooiman introduced here offers an analytical framework that uses the concept of "governability." It is a measure of how governable a particular social system is that takes care of a public function. Assessment is facilitated by breaking down and describing the social system into constituent parts and by exploring the properties, qualities, and the way in which they interact with each other. Further, by deliberating a complex public health function such as immunization services in the context of developing countries, we explore the application of the interactive governance theory and governability. Conclusion: The theory offers new insights into how interactive and holistic approaches can be integrated into public health practice. The advantage of the concept of "governability" is that it enables us to explore why some governance systems deliver what they are expected to, while others do not. This might help us to identify areas where governance can be improved. (Contains 1 table and 1 figure.)