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Digital Documentation of COVID-19 Certificates (DDCC)

The Digital Documentation of COVID-19 Certificates (DDCC) published in August 2021 and similar guidance for test results (https://www.who.int/publications/i/item/WHO-2019-nCoV-Digital_certificates_diagnostic_test_results-2022.1) published in March 2022 serve as the reference for the associated FHIR Implementation Guide. This Implementation Guide (IG) acts as the computable representation of the core data elements in the published guidance, mapped to standard terminologies. These data models, in the form of FHIR logical models, and terminologies, in the form of FHIR value sets, are the basis for interoperability between the various credential formats. The IG provides FHIR Structure Maps and Concept Maps to define transformations between supported credential formats and the core data set, which allows business rules to execute against a common set of data elements.

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Strategy for mapping COVID certificate terminologies to the DDCC core data sets​

Test result​

The core data set (FHIR.WHO.DDCC\DDCC Core Data Set Logical Model for Test Result) has bindings to the following terminology:

Cert. typeElementCore data mappingApproach
DIVOCevidence.diseasepathogenMap custom code system to ICD-11
DIVOCevidence.testTypetypeMap custom code system to ICD-11
DIVOCevidence.sampleOriginoriginMap custom code system to ICD-11
DIVOCevidence.resultresultMap custom code system to ICD-11
DIVOCevidence.facility.address.addressCountrycountryISO-3166 two or three character
EU DCC-260.t.tgpathogenMap SNOMED CT to ICD-11
EU DCC-260.t.tttypeMap generic LOINCs to ICD-11
EU DCCNot presentoriginn/a
EU DCC-260.t.trresultMap SNOMED CT to ICD-11
EU DCC-260.t.tocountryISO-3166 two character
ICAONot presentpathogenn/a
ICAOdata.msg.tr.tctypeMap custom code system to ICD-11
ICAOdata.msg.tr.moriginMap custom code system to ICD-11
ICAOdata.msg.tr.rresultMap custom code system to ICD-11
ICAOdata.msg.sp.ctrcountryAssuming ISO-3166 three character
SHCInferred from codepathogenAssume COVID-19 if LOINC listed here
SHCcode*typeMap LOINC to ICD-11
SHCNot currently present, but will be bodySite*originn/a
SHCvalueCodeableConcept.coding[0].code*resultMap SNOMED CT to ICD-11

* Note that these elements are within the FHIR Bundle that is part of the SMART Health Card. The full path to this is vc.credentialSubject.fhirBundle.entry[].resource.

Proof of vaccination​

The core data set (FHIR.WHO.DDCC\DDCC Core Data Set Logical Model - Vaccination Status - Proof of Vaccination) has bindings to the following terminology:

  • Vaccine (vaccine):
    ICD-11 MMS codes for both types of vaccine (e.g., XM5DF6 COVID-19 vaccine, live attenuated virus) and specific vaccine products (e.g., XM3DT5 COVID-19 Vaccine Moderna)

  • Vaccine brand (brand):
    Not currently bound to a ValueSet

  • Country of vaccination (country):
    Three character country codes - Valueset-iso3166-1-3

Mapping approach​

Cert. typeElementCore data mappingApproach
DIVOCevidence.icd11CodevaccinePresumably already ICD-11 MMS (see below)
DIVOCevidence.facility.address.addressCountrycountryISO-3166 two or three character
EU DCC-260.1.v.mpvaccinePreferred binding is Union Register, but could also be ICD-11 or arbitrary strings. Only Union Register is considered in our mapping code.
EU DCC-260.1.v.cocountryISO-3166 two character
ICAOdata.msg.ve.desvaccineAlready ICD-11 MMS
ICAOdata.msg.ve.vd[].ctrcountryAlready ISO-3166 three character
SHCvaccineCode.coding[0].code*vaccineICD-11 MMS, CVX, or SNOMED CT; latter two mapped to ICD-11 MMS
SHCNot present in computable formcountryn/a

* Note that these elements are within the FHIR Bundle that is part of the SMART Health Card. The full path to this is vc.credentialSubject.fhirBundle.entry[].resource.

FHIR Resource naming conventions​

ValueSets​

  • Lab test - pathogen (COVID-19):
    • name: LabTestPathogenCovid19{TerminologyName}ValueSet
    • id: lab-test-pathogen-covid19-{terminology-name}
    • title: Lab Test - Pathogen - COVID-19 - {Terminology Name}
  • Lab test - type (COVID-19-specific):
    • name: LabTestTypeCovid19{TerminologyName}ValueSet
    • id: lab-test-type-covid19-{terminology-name}
    • title: Lab Test - Type - COVID-19 - {Terminology Name}
  • Lab test - type (generic):
    • name: LabTestType{TerminologyName}ValueSet
    • id: lab-test-type-{terminology-name}
    • title: Lab Test - Type - {Terminology Name}
  • Lab test - sample origin:
    • name: LabTestSampleOrigin{TerminologyName}ValueSet
    • id: lab-test-sample-origin-{terminology-name}
    • title: Lab Test - Sample Origin - {Terminology Name}
  • Lab test - qualitative result:
    • name: LabTestQualitativeResult{TerminologyName}ValueSet
    • id: lab-test-qual-result-{terminology-name}
    • title: Lab Test - Qualitative Result - {Terminology Name}
  • Vaccine (COVID-19):
    • name: VaccineCovid19{TerminologyName}ValueSet
    • id: vaccine-covid19-{terminology-name}
    • title: Vaccine - COVID-19 - {Terminology Name}

FSH filenames should be tx-vs-{id}.fsh. Each ValueSet should be in a separate file.

All ValueSet descriptions should describe where the codes in the value set came from and when the snapshot was taken. This should have enough information for someone to verify the contents of the value set or update it using the same approach.

The goal is that name should clearly identify both the resource type and contents when used in FSH within this IG, and the canonical URI (based on id) should not have any redundant information in it. The title should not include the resource type as this is implicit in how the resources are displayed in the IG.

Terminology names in ids should be shortened as much as possible while still being readable. For example, SNOEMD CT becomes snomed; ICD-11 becomes icd11.

"COVID-19" should appear in id/name/title when using a COVID-specific subset of a broader terminology system. For internally defined code systems (like those used by DIVOC and ICAO), "COVID-19" should not appear in case those specifications are expanded in the future (otherwise it would be necessary to create a 2nd value set, which would be problematic for terminology bindings in the logical model).

CodeSystems​

Code systems are included to allow for expansion.

FSH filenames should be tx-cs-{alias}.fsh, like tx-cs-snomed.fsh. Each CodeSystem should be in a separate file. In cases where the IG already has a code system defined, the codes should be merged into the existing system rather than placed in a separate file.

ConceptMaps​

In the naming scheme below:

  • $type = LabTestPathogenCovid19/lab-test-pathogen-covid19/Lab Test - Pathogen - COVID-19, etc.; for vaccines it is VaccineCovid19/vaccine-covid19/Vaccine - COVID-19
  • $source = terminology name for the source terminology
  • $target = terminology name for the target terminology

With these variables defined, ConceptMaps should be named as follows:

  • name: {$type}{$source}To{$target}ConceptMap
  • id: {$type}-{$source}-to-{$target}
  • title: {$type} - mapping {$source} to {$target}

For example, if:

  • $type = Vaccine - COVID-19 (and variants)
  • $source = CVX
  • $target = ICD-11

...then we would have:

  • name: VaccineCovid19CVXToICD11ConceptMap
  • id: vaccine-covid19-cvx-to-icd-11
  • title: Vaccine - COVID-19 - mapping CVX to ICD-11
  • Filename: tx-cm-vaccine-covid19-cvx-to-icd-11.fsh

Each ConceptMap should be in a separate file.

Source specifications​

It can be difficult to find the "source of truth" specifications for the certificate formats that are mapped to the DDCC core data sets. The following are links to the best known documentation for each of the certificate formats listed above: