Around the world, various different coding systems are used for immunizations:

<status value="active"/><experimental value="false"/><publisher value="HL7 FHIR"/><contact><telecom><system value="url"/><value value="http://hl7.org/fhir"/></telecom></contact><description value="This identifies the vaccine substance administered - CVX codes."/><jurisdiction><coding><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><compose><include><system value="http://hl7.org/fhir/sid/cvx"/></include><include><system value="urn:oid:1.2.36.1.2001.1005.17"/></include></compose></ValueSet>