This is the ValueSet that contains all the codes in Immunization Subpotent Reason (http://hl7.org/fhir/ValueSet/immunization-subpotent-reason) and Immunization Subpotent Reason (http://hl7.org/fhir/ValueSet/immunization-subpotent-reason). E.g. what you have to deal with if you get resources containing codes in either of them