f:Immunization extension with URL = 'https://fhir.hl7.at/elga/aps/r4/StructureDefinition/at-aps-ext-immunization-basedOn': maximum cardinality of 'extension' is 1 protocolApplied: minimum cardinality of 'protocolApplied' is 1 f:Immunization/f:protocolApplied targetDisease: minimum cardinality of 'targetDisease' is 1