HL7 VXU_V04 Vaccination Record Update

How EHRs and immunization systems send administered vaccine records.
HL7 message structure VXU_V04 groups and segments from HL7 v2.5.1 Hide structure

These are the generated groups and segments for the version selected at the top of the page. The article explains the workflow, and this panel follows the chosen HL7 version.

Message Structure

SegmentNameRequiredRepeatable
MSH
 Message Header Yes No
SFT
 Software Segment No Yes
PID
 Patient Identification Yes No
PD1
 Patient Additional Demographic No No
NK1
 Next of Kin / Associated Parties No Yes
VXU_V04.PATIENT
 Patient group No No
PV1
 Patient Visit Yes No
PV2
 Patient Visit - Additional Information No No
GT1
 Guarantor No Yes
VXU_V04.INSURANCE
 Insurance group No Yes
IN1
 Insurance Yes No
IN2
 Insurance Additional Information No No
IN3
 Insurance Additional Information, Certification No No
VXU_V04.ORDER
 Order group No Yes
ORC
 Common Order Yes No
VXU_V04.TIMING
 Timing group No Yes
TQ1
 Timing/Quantity Yes No
TQ2
 Timing/Quantity Relationship No Yes
RXA
 Pharmacy/Treatment Administration Yes No
RXR
 Pharmacy/Treatment Route No No
VXU_V04.OBSERVATION
 Observation group No Yes
OBX
 Observation/Result Yes No
NTE
 Notes and Comments No Yes

VXU_V04 is the unsolicited vaccination record update message. In practice, an EHR, pharmacy system, clinic system, or immunization module sends it to an immunization information system, registry, public health endpoint, or integration engine to report administered vaccines and related patient data.

VXU is one of those messages where the base structure is only the start. National and regional immunization implementation guides define much of the real behavior: required patient demographics, responsible organization, vaccine coding, administered amount, lot, funding, eligibility, refusal, history, and ACK error handling.

A small VXU example

MSH|^~\&|EHR|CITYCLINIC|IIS|STATE|20260715170000||VXU^V04^VXU_V04|VXU00004|P|2.5.1 PID|1||123456^^^CITYCLINIC^MR||Smith^Jamie^^^^^L||20190514|F|||12 High Street^^Auckland^^1010^NZ^H PD1|||||A NK1|1|Smith^Jane|MTH|12 High Street^^Auckland^^1010^NZ^H|^PRN^CP^^64^21^5551234 ORC|RE||IMM20260715001^EHR RXA|0|1|20260715100000||140^Influenza, seasonal injectable^CVX|0.5|mL||00^New immunization record^NIP001|12345^Nurse^Nora|^^^CITYCLINIC||||A12345|20271231|SANOFI^Sanofi^MVX RXR|C28161^Intramuscular^NCIT|LA^Left arm^HL70163 OBX|1|CE|64994-7^Vaccine funding program eligibility category^LN||V01^Not VFC eligible^HL70064||||||F

What systems do with it

The receiver matches the patient, validates the vaccine event, checks required registry fields, stores or updates the immunization record, and sends an ACK. In many IIS workflows, the ACK is not just transport feedback; it is how the sender learns that a vaccine code, lot, eligibility value, patient field, or organization identifier needs correction.

PID and PD1 carry patient and registry-relevant demographic detail. ORC groups each administered vaccine event. RXA is the administration itself, RXR is the route/site, and OBX carries profile-defined observations such as funding, eligibility, history indicators, or contraindication-style details.

How to read the structure

The v2.5.1 structure starts with patient identity, then optional visit, guarantor, and insurance context. The order group repeats, and each order group requires ORC and RXA. RXR and OBX sit under the order because they describe that vaccine event.

Do not assume every RXA is an administered dose in the same way. Immunization guides often distinguish administered, historical, refused, or not-administered records through RXA and OBX values. The receiver's guide is authoritative for those details.

Implementation traps

Vaccine coding is usually the first place to be strict. CVX, MVX, lot number, expiration date, dose amount, route, site, administering provider, and responsible organization all need profile-specific care. A VXU that "looks right" can still be rejected if one coded value belongs to the wrong value set.

Also treat ACK errors as data-quality feedback. Retrying an invalid VXU without fixing it only proves the transport works. Integration Soup can route these ACKs into operational queues so the team sees the correction, not just the failed send.

Reference notes

CDC notes that the consolidated HL7 v2.5.1 Implementation Guide for Immunization Messaging is the current CDC/AIRA-recognized standard for immunization messaging. See CDC IIS HL7 guidance and local IIS guides for exact VXU field requirements.