Interoperability is often described as the ability to move information from one system to another. That is essential, but successful delivery does not guarantee shared understanding.
Imagine that a system receives a vaccine code. It may be able to store the code correctly and send it on again. But can it determine which vaccine the code represents, what diseases it targets, how it relates to codes in another system, or whether it describes a product that is no longer routinely used? Without that information, the code can travel farther than its meaning.
This is particularly important for immunization histories. A code set designed only around vaccines currently authorized in one place may seem complete for today's workflow. It may still be unable to represent a vaccination given last year, decades ago, or in another country. The missing information becomes a practical problem when records are exchanged, consolidated, or interpreted later.
Rich reference information is therefore not decoration around a code system. It is part of the infrastructure that makes the codes useful. Concepts need clear definitions, relationships, stewardship, and histories that can be referenced consistently. Exchange standards can carry information, but they cannot create shared meaning when that meaning has not been organized and maintained.
This principle shapes the work of the Immunization Vocabularies Collaboration. We support the people who build and maintain vaccine code sets by helping make vaccine concepts easier to understand, compare, and align. The goal is not to replace every local vocabulary with a single code system. It is to make the meaning represented by those systems richer and easier to use across contexts.
Tito Castillo explores the wider architectural version of this problem in FHIR Is Not the Problem. But We May Be Asking It to Solve the Wrong One. His article asks whether healthcare keeps placing meaning inside exchange specifications when authoritative definitions and reference data should be managed as infrastructure in their own right. It is a useful frame for why vaccine vocabulary work matters.