Digital Health

Strategies to Address Multiple Patients Matched in an Immunization Query

Health professional typing at a work station.

What are multiple/inexact matches?

One of the major benefits of connecting electronic health record (EHR) systems to public health immunization information systems (IIS) is the ability to obtain a patient’s immunization history consolidated from various health care providers and a forecast for needed vaccinations. The ability to query an IIS for a patient’s vaccination information is dependent on an IIS’ ability to correctly match a patient from the EHR’s query to their IIS record. Inexact matches occur when an IIS has low confidence in a single potential match or when an IIS identifies more than one potential match (i.e., multiple matches). The inability to properly match patients may adversely impact patient care (under/over vaccinated) and waste limited resources (e.g., vaccine product, health care provider and patient time). Obtaining estimates for inexact match rates is difficult as many health information technology systems do not retain query-response message data in a manner conducive to the type of analysis described below. However, this information would be beneficial to review if query response data is available. With a limited set of sample data (12 sites within 12 different states) from one EHR vendor, the rate at which IIS returned inexact matches in response to queries was variable, but ranged from 0.13% to 26.41%. Within these data, the median of the inexact match response was 1.30%. Although there may be relatively low prevalence of inexact matches, given the large query volume of IIS (246 million in 2019), millions of queries may result in inexact matches.

Why do multiple/inexact matches occur?

Multiple/inexact matches can occur for several reasons, including:

  • Common names
  • Providing limited data in queries (e.g., middle name missing)
  • The appearance of a single patient multiple times (i.e., duplicate patients) within an IIS
  • Out-of-date information in an EHR or IIS (e.g., patient changes names or moves)

What happens when multiple/inexact matches occur and why is it important?

After a query is initiated by an EHR user, an IIS may return a listing of patient demographics for one or more potential matches. Some EHRs allow users to review these demographics and execute a second query with updated patient demographics parameters or the IIS patient ID with the expectation that the more complete query will result in a single high-threshold match and the return of associated clinical data for the patient. EHRs that allow display of multiple/inexact matches may require additional provider workflow steps to issue a second query to retrieve the patient’s immunization history and forecast. This ultimately results in improved patient care, but may require additional provider time. Some EHR implementations do not allow users to review multiple/inexact matches or adjust query parameters to perform a subsequent query. In such cases, the clinician does not receive an immunization history or recommendation from the IIS for the patient and must either proceed with clinical care without that information or access the patient’s IIS record through an alternate means, such as leaving the context of the EHR to search through an IIS web portal.

What do healthcare administrators and IIS managers need to know and what can be done to reduce multiple/inexact matches?

It is critical that healthcare administrators and IIS managers are aware of the pervasiveness of inexact matches, underlying data quality issues (completeness, timeliness, accuracy) that may lead to inexact matches, and functionality within EHRs and IIS that can best support users attempting to obtain patient information from IIS. ​​The Immunization Integration Program convened a workgroup to assess the current state and gain agreement on recommendations to improve the way in which multiple/inexact patient matches from a query to an IIS are handled among clinicians and clinical software systems, thus requiring additional workflow efforts to retrieve individual patient immunization histories and forecasts. The workgroup’s resources include the Query Response Aggregate Measurement Document and the Query Response Workflow Functionalities Catalog. These documents could be utilized to develop reports to evaluate inexact matches and determine which functionalities could be implemented to address identified issues.

What is the IIP Query Response Aggregate Measurement Document?

The Immunization Query Response Aggregate Measures for Multiple Matches Report provides metrics to assess query response outcomes. Health information technology developers can assist users by creating new functionality that allows users to generate aggregate query-response reports. Practice and IIS administrators can use these metrics to identify areas of concern and analyze performance trends over time. Once an issue reaches a critical threshold (as determined locally), system administrators may wish to investigate further and develop an improvement plan. The three sets of metrics included are “basic,” “query parameter completeness” and “advanced.” These metrics are a starting point to determine if an issue is present. 

What is the IIP Query Response Workflow Functionalities Catalog?

The Immunization Query Response Workflow Functionalities Catalog identifies the potential query outcomes an EHR end user or provider may be faced with, the possible follow-up actions to take and EHR and IIS functions needed to help the user address each situation. The document is intended to improve awareness and provide guidance to healthcare information technology (HIT) vendors. These cataloged functionalities will help health information and technology system developers determine which functionalities might provide the most helpful approach for their specific settings.  

What can decision-makers do to help improve outcomes of multiple/inexact matches?

  • Improve understanding of how multiple/inexact matches and associated EHR functionality can impact patient care
  • Assess the current state of multiple/inexact matches of their healthcare settings, including what patient data from the IIS is not accessible to providers and how much time such users spend reviewing multiple/inexact matches
  • Evaluate client systems periodically with appointed person (e.g., IT developer) to determine if additional functionality should be implemented, ideally by comparing performance metrics over time
  • Share and discuss the IIP’s Immunization Query Response Aggregate Measures for Multiple Matches Report and the Immunization Query Response Workflow Functionalities Catalog with your organization’s interoperability lead
  • Connect with the IIP at to discuss a spectrum of technical assistance opportunities or strategies for piloting the recommended solutions

What limitations exist related to these solutions?

  • The workgroup’s focus was not to eliminate multiple/inexact matches, but rather improve awareness and guidance for handling these occurrences
  • Poor data quality (e.g., incomplete or duplicate patient data) negatively impacts the rate of multiple/inexact matches
  • Reasons for multiple/inexact matches may be out of the control of the querying system—no matter how well equipped, if the matching algorithm is poor the matching quality will be poor as well
  • Proposed functionalities (e.g., EHR users notifying IIS of potential duplicate) may be dependent on future enhancements to EHR and IIS systems and workflow changes
  • Use of functionalities is dependent on the environment - not all functionalities will be appropriate for all settings (e.g., large organization v. small organization)
  • Each organization must consider the benefits gained (e.g., complete patient immunization information) v. the cost (e.g., additional training and software development)
  • Some jurisdictional and organizational policies do not permit multiple/inexact matches candidate listing to be shared or reviewed


Immunization Query Response Aggregate Measures for Multiple Matches Report

In February 2020, the Immunization Integration Program (IIP) Executive Committee identified four areas of focus from over 30 prioritized issues for improving immunization interoperability, information sharing and management.

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