How a state health department deployed an immunisation tracking and reporting platform at the scale of 2 million patient records — the technical architecture that made it possible, and the public health impact achieved.
Get StartedState and provincial immunisation registries are among the most consequential public health information systems in existence — the operational foundation for childhood immunisation programs, flu campaigns, pandemic response, and school-entry compliance.
Building one at the scale of millions of records, across hospitals, private clinics, pharmacies, school health programs, and public health departments, is a substantial health informatics undertaking with direct public health consequences when it works poorly.
The legacy registry was built more than 15 years before the replacement decision. Repeatedly extended and patched, it retained fundamental architectural limits: provider data submission was mostly manual file uploads in formats that varied by provider type, with no standardized electronic pathway and no real-time bidirectional EHR connectivity.
The result was persistently incomplete, delayed data. An immunisation given at a private practice might not appear for two to four weeks. Manageable for school-entry checks — but a serious vulnerability for pandemic response requiring rapid assessment of population vaccination status.
Providers consistently reported submission as burdensome and error-prone. Each organization built its own extract-and-upload process, maintained it as EHRs changed, and troubleshot errors without health-department support. Many smaller and rural providers had simply stopped submitting.
Up to 15 years of immunisation history had to move to preserve longitudinal records. An 8-month migration ran in parallel with the build — remediating data quality, migrating in validated batches, and synchronizing the final batch to go-live.
A dedicated outreach program — not mandates — drove adoption: direct technical assistance, webinar training, and per-system guides. The web portal was positioned as the lowest barrier, completing a record in under two minutes.
FHIR direct submission plus CSV and HL7 v2 pathways meant every provider, regardless of technology, had an accessible mechanism — reversing the legacy drop-off and reaching a 94% real-time submission rate within the first year.
Role-based access via the state identity infrastructure scoped each user type — clinicians to their patients, public health to de-identified aggregates, schools to compliance status only — with a full, regularly reviewed audit trail.
The shift from delayed batch submission to real-time FHIR transformed the registry into a clinical decision-support tool — current at the point of care rather than weeks out of date.
Within six months, 94% of immunisations from participating providers appeared in the registry within minutes of administration rather than days or weeks.
Pediatric and family medicine practices query the registry at well-child visits to verify status instead of relying on parent-reported history — catching gaps missed in previous visits.
Childhood immunisation coverage improved measurably in the year after go-live, attributable in part to the better registry data's ability to identify and close gaps.
During a regional campaign eight months post-launch, peak daily volume hit ~4x normal as community events submitted en masse — handled without service degradation.
