The FHIR R4 Immunization resource captures details about vaccines administered to a patient. It includes information about the vaccine type, dosage, administration details, and other relevant data. This resource helps healthcare providers track immunization history and ensure patients receive appropriate vaccinations.

Health Gorilla exposes Immunization as part of its FHIR R4 API to support patient-centric tracking of vaccination history and administration details.

Use Cases

Recording vaccine administration for a patient
Retrieving immunization history for a patient
Updating immunization details for ongoing vaccination plans

Scope and Behavior

This documentation describes the FHIR R4 API interface for Immunization. Health Gorilla’s platform may use additional internal services and data standards to acquire, normalize, and route clinical information. Only the FHIR R4–exposed behavior is documented here.

Health Gorilla supports a subset of the HL7 FHIR R4 Immunization resource. Not all optional elements defined in the HL7 specification may be stored, indexed, or returned. Unsupported or unrecognized elements may be ignored or normalized during processing.

In Health Gorilla, Immunization is most commonly accessed as part of patient record retrieval workflows, where vaccination data may be aggregated from connected clinical systems and normalized for longitudinal review. This resource supports preventive care tracking, compliance reporting, and public health documentation use cases.

Authentication

All requests to the FHIR R4 API require OAuth 2.0 authentication using a bearer token. Unauthorized requests return 401 Unauthorized responses.

Required Scopes:

immunization.read for GET
immunization.write for POST, PUT, DELETE

For more information, go to: OAuth 2.0 Authentication.

Search Behavior

Searches are scoped to the authenticated tenant. The patient parameter is required for patient-scoped searches and is recommended for most search use cases.

Results are returned as a FHIR Bundle. Pagination may be applied. Use standard FHIR pagination links (Bundle.link) to retrieve additional result pages.

Note: The parameters listed below are not exhaustive and reflect commonly used fields in typical Health Gorilla workflows. Supported parameters and behavior may vary by configuration.

Frequently Used Search Parameters

Parameter	Description	Example Values	FHIR Data Type
`patient`	Filters by patient	`Patient/{id}`	`Reference`
`date`	Filters by administration date	`ge2022-01-01`, `le2023-12-31`	`date`
`vaccine-code`	Filters by vaccine code	SNOMED CT or CVX codes	`token`
`status`	Filters by immunization status	`completed`, `entered-in-error`	`token`
`manufacturer`	Filters by vaccine manufacturer	`Organization/{id}`	`Reference`
`lot-number`	Filters by vaccine lot number	`AB12345`	`token`
`encounter`	Filters by related encounter	`Encounter/{id}`	`Reference`
`location`	Filters by administration location	`Location/{id}`	`Reference`
`status-reason`	Filters by reason for current status	SNOMED CT codes	`token`

Commonly Returned Resource Attributes

Attribute	Description	Example Values	FHIR Data Type
`patient`	Reference to the patient who received the immunization	`Patient/{id}`	`Reference(Patient)`
`vaccineCode`	Vaccine administered	SNOMED CT or CVX code	`CodeableConcept`
`status`	Current status of the immunization	`completed`, `entered-in-error`	`code`
`occurrenceDateTime`	Date and time when the immunization was administered	`2022-01-01T12:00:00Z`	`dateTime`
`lotNumber`	Lot number of the administered vaccine	`AB12345`	`string`
`manufacturer`	Vaccine manufacturer	`Organization/{id}`	`Reference(Organization)`
`encounter`	Encounter during which immunization was administered	`Encounter/{id}`	`Reference(Encounter)`
`location`	Location of administration	`Location/{id}`	`Reference(Location)`
`performer`	Who administered the vaccine	`Practitioner/{id}`, `Organization/{id}`	`BackboneElement[]`
`note`	Additional notes	Annotation entries	`Annotation[]`
`reaction`	Reaction details following immunization	Structured reaction entries	`BackboneElement[]`

Notifications

The FHIR R4 API does not provide direct resource-change subscriptions for Immunization. Changes to immunization information may surface through broader notification workflows, depending on enabled Health Gorilla products and configuration.

Error Handling

All Immunization operations follow standard Health Gorilla error handling, including use of FHIR OperationOutcome for structured responses. For more information, go to: Error Handling.

Additional Resources

HL7 FHIR Immunization Resource