FHIR R4 Immunization resource example

Immunization records one dose given (or not given). The vaccine is coded in vaccineCode; in the United States that is usually a CVX code.

The Immunization in JSON

{
  "resourceType": "Immunization",
  "id": "flu-2026",
  "status": "completed",
  "vaccineCode": {
    "coding": [
      {
        "system": "http://hl7.org/fhir/sid/cvx",
        "code": "141",
        "display": "Influenza, split virus, trivalent, preservative"
      }
    ],
    "text": "Flu vaccine"
  },
  "patient": {
    "reference": "Patient/example",
    "display": "Jane Doe"
  },
  "occurrenceDateTime": "2026-10-05",
  "primarySource": true,
  "lotNumber": "FL2026-118",
  "site": {
    "coding": [
      {
        "system": "http://terminology.hl7.org/CodeSystem/v3-ActSite",
        "code": "LA",
        "display": "left arm"
      }
    ]
  },
  "doseQuantity": {
    "value": 0.5,
    "unit": "mL",
    "system": "http://unitsofmeasure.org",
    "code": "mL"
  }
}

Validator result: raw JSON · open the validator

informationNo errors: this Immunization matches the FHIR R4 structure checked here.

The elements that matter

Element	Cardinality	Notes
`status`	1..1	`completed`, `entered-in-error` or `not-done`.
`vaccineCode`	1..1	The vaccine product.
`patient`	1..1	The person vaccinated.
`occurrence[x]`	1..1	`occurrenceDateTime` or `occurrenceString`.
`lotNumber`	0..1	Batch, useful for recalls.

The full definition is in the FHIR R4 Immunization specification.

Common mistakes and the errors they cause

Status outside the value set

given is not an Immunization status.

errorImmunization.statusImmunization.status 'given' is not in the required value set (completed, entered-in-error, not-done).

Missing occurrence

occurrence[x] is 1..1: a dose has a date.

errorImmunizationOne of these elements is required: occurrenceDateTime, occurrenceString.

Date in a local format

FHIR dates are ISO 8601.

errorImmunization.occurrenceDateTimeNot a FHIR dateTime: YYYY, YYYY-MM, YYYY-MM-DD or YYYY-MM-DDThh:mm:ss with a time zone (Z or +hh:mm).

Store it in a real FHIR R4 serverA free sandbox key gives you 30 synthetic patients and the full API, including POST /fhir/R4/Immunization and $validate.

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More examples

Related guides

How to store medical records using FHIR R4Tutorial: create a Patient, a blood-pressure Observation and a Condition, use a transaction, search, update with history and read provenance — every request with curl and the real response, on the free sandbox.