HL7 v2 Reference

Testing HL7 v2 RXA-5: What Administered Code Actually Needs to Handle

Jul 27, 2026 · 4 min read

RXA-5 is the field that says what was actually administered. Immunization registries live and die on this one being coded correctly against CVX, so a bad mapping here is a bad mapping everywhere downstream.

Quick answer

RXA-5 is a coded element (CE/CWE) identifying the drug or vaccine administered. For immunizations it typically carries a CVX code; pharmacy administration feeds may instead use NDC, RxNorm, or a local formulary code, sometimes alongside a CVX equivalent in repeating components.

What this field contains

CVX

CDC vaccine code table — the dominant code system for VXU immunization messages, e.g. 08 for Hepatitis B, adult formulation

NDC

National Drug Code — common in pharmacy administration feeds tied to a specific manufacturer/package

Local/formulary code

Site-specific code — some source systems send an internal drug code that must be mapped before it means anything outside that facility

Example

Synthetic example Generated by Synthibase

RXA|0|1|20260726090000||08^Hep B, adult^CVX|0.5|mL^^UCUM|||||||||||CP|A

RXA-5 carries 08^Hep B, adult^CVX — code, text, and coding system components for a synthetic Hepatitis B administration.

Where this trips people up

Multiple coding systems can legally coexist here through repetition, and test data generators that only ever produce a single clean CVX component miss the parsing bugs that show up when a source system sends CVX and NDC together, or sends an unrecognized code from a coding system your mapping table doesn't cover. It is also easy to overlook that the descriptive text component is not authoritative — systems that trust the text over the code end up with mismatched vaccine names when a code is right but a vendor's free-text label is stale.

→

HL7 v2 RXA Segment Guide: Fields, Format, and Testing Gotchas

→

Synthetic Patient Data: Complete Guide for Software Testing

→

Healthcare API Testing Guide: FHIR and X12

Test against realistic CVX and NDC combinations

Synthibase generates RXA segments with correctly-mapped, varied administered codes — including multi-coding-system repetitions — so your mapping logic gets tested the way it will actually be used in production.

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This page is written independently by Synthibase for testing and informational purposes. It is not an official publication of HL7 International or X12/Washington Publishing Company, and is not a substitute for reviewing the official standard or your trading partner's companion guide. See our Terms of Service for full legal terms.