The Immunization resource contains a reference to an Organization that is the vaccine manufacturer. This element has a cardinality of 0..1. However, the reality of situation is that there are sometimes multiple organizations who can be thought of as a manufacturer. There is the organization who manufactures the vaccine, but there are sometimes other organizations who act as distributers or relabelers. Another example is where a company is acquired by another company but maintains a discrete presence in the new owner (eg. IDB was acquired by GSK but maintained an independent existence for a period of time and it would have been helpful to be able to send both organizations in a resource). Depending on the use case, it may be necessary to document multiple types of manufacturers along with the Organizations who played a given role. 

It would be helpful if .manfuacturer was transformed into a backbone element that contained a CodeableConcept manufacturerRole (maker, distributer, etc) and a reference to an Organization.

The value set for the role element could be just an example value set unless we have a clear set of values.