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SOAP Standard Interface: Case Studies of SOAP Implementation

The Transport Layer Expert Panel, in support of their recommendation of SOAP (Simple Object Access Protocol) as the standard for immunization data exchange, is collecting case studies from those who have implemented the SOAP interface.

NYC HL7 SOAP Web Service Case Study

October 2011


The New York Citywide Immunization Registry (CIR) is an Immunization Information System that serves health care providers, parents and data exchange partners authorized by the DOHMH to retrieve of immunization records, to ensure that individuals receive all required immunizations. As of April 2011 there are 241 public immunization facilities and 1,574 private immunization sites in NYC that vaccinate children and adolescents. The two principal sources of CIR data are birth certificates (loaded weekly) and data supplied by providers who are required by the NYC Health Code and New York State Public Health Law to report immunizations administered to children 0-18 years of age. More than 90% of enrolled NYC childhood immunization providers report regularly and an estimated 88% of immunizations given in NYC are reported within 30 days of administration [1].

In the spring of 2007, the CIR partnered with HLN Consulting, LLC (HLN) and the Primary Care Information Project (now called the Regional Extension Center for NYC), to implement a real time, bi-directional HL7 Web Service for immunization transactions, in accordance with the CDC’s Health Level 7 (HL7) implementation guide [1]. CIR deployed the HL7 version 2.3.1 Web Service in production in the summer of 2009.

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Development of CIR’s Web Services

One of the primary considerations involved in the selection of data communication middleware is the ease with which EHR systems can integrate with the technology. The CIR found SOAP Web Services to be a good fit for this requirement, because it integrates easily with Microsoft’s .NET framework and Java, primary software development environments used by EHR vendors. An additional benefit is that highly competitive, free, open source SOAP application server implementations are available, an important consideration at a time when budgets are in decline. As the Web Service was being developed, HLN and CIR staff recognized the need for a technical guide for the EHR vendors and hospital IT staff programming a CIR interface. Intended as a supplement to the CDC’s Implementation Guide for Immunization Data Transactions using Version 2.3.1 of the HL7 Protocol [2], the CIR HL7 2.3.1 Integration Guide [3] provides CIR-specific requirements for connecting to the registry’s HL7 Web Service and for creating proper messages. The CIR’s HL7 Integration Guide also includes detailed examples, containing sample HL7 messages in their entirety and in detail, along with the CIR response.

Interface Development, Testing and Certification

After giving partners time to review the integration guide, the CIR works closely with vendor and hospital IT teams during their development and implementation process. During bi-weekly conference calls, CIR staff review the design and implementation of the EHR, including the data fields that will be sent, how immunization histories and decision support information returned from queries will be displayed and stored, and how errors will be handled.

All EHR vendors are required to participate in a formal CIR quality assurance process before they can deploy real-time data exchange for their clients in production. Each vendor must undergo an official test in which they select a pilot site from which to send real immunization data--usually one month’s worth. The data is sent to the Web Service test environment as individual HL7 transactions, which are reviewed by CIR staff within 48 hours. CIR then provides feedback on the message statistics (how many were successful, partially successful or failed), explanations of the observed errors, and suggestions for correcting those errors. Once the vendor has had time to make corrections, they are asked to send another sample of real data to the test environment to confirm that all known issues have been resolved and that no new errors were introduced. If this test is successful, they are certified to begin rolling out the production interface to their clients; if not, the testing process is repeated until all outstanding errors are resolved.

Data Quality Assurance

When the CIR HL7 Web Service was being developed, a database audit trail was designed to support the analysis of inbound HL7 requests. The audit trail tables allow data analysts to perform ad-hoc checks of the reporting and querying activity of any healthcare facility in NYC. To decrease the workload associated with reviewing messages for data quality, and to make such review accessible to less technical staff, the CIR worked with its private partner for software development, HLN, to develop a tool to automate much of the process. This tool, called the CIR Administrative Tool (CAT), is a Web-based data exchange management application that enables CIR staff to perform data quality assurance.

CAT allows CIR staff to search all of the HL7 messages sent by a particular facility during a specified time period. The user can see whether individual messages were accepted, rejected, or partially rejected, and review the errors that caused messages to be rejected. Staff can compile statistics on error types and message success/failure rates and view the individual HL7 messages that contributed to the selected statistic. CAT is also used to drill down to the message level and view the field values, making it possible to pinpoint errors or missing data elements.

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Completed Integrations

The Columbia Presbyterian Hospital network was first to query the Web Service in July 2009 and to date has sent close to 700,000 queries for patient immunization histories. In a random sample of children who received medical care at Columbia Presbyterian, the vaccine coverage rates increased from 79.3% to 85.6% for 7-23-month-olds and from 78.6% to 86.1% for 24-36-month-olds, when the CIR HL7 Web Service was queried for additional information. Documented coverage for the adolescent immunization series increased from 74.5% to 79.3% for Tdap, 69.8% to 76.4% for MCV4, and 61.1% to 68.0% for HPV1, showing that integration with the CIR increases patient documented up-to-date rates by several percentage points. [4]

The Health and Hospitals Corporation, New York City’s large public hospital and health care facility network, is testing their integration with the CIR Web Services and will begin rolling out their interface at individual facilities in May of 2011. While their initial interface is unidirectional, they plan to implement bi-directional communication shortly. This partnership is very important in NYC, because HHC facilities alone reported close to 650,000 immunizations in 2010, accounting for almost 10% of the total immunizations added to the CIR. As of April 2011, one EHR vendor has completed CIR’s testing and quality assurance process and has rolled out the interface to 27 of their private provider facilities. These facilities have used the HL7 Web Service to report more than 68,000 immunizations and perform more than 9,000 queries.


While MU has provided a powerful impetus for EHR vendors to work with IIS, progress has been hindered by the limitations of the MU requirement for immunization reporting. EHR vendors are eager to comply with the MU criteria, which at this stage only require unidirectional communication from the provider’s EHR to the CIR. Few EHR vendors at this time are willing to undertake the work required to implement bi-directional communication. This is unfortunate, because much of the value of the interface for healthcare providers lies in the ability to receive immunization histories and decision support from an IIS.

An additional challenge is the number of EHR vendors and products utilized by NYC providers. Each vendor requires a separate development effort and a significant investment of time and resources, whether the vendor has 500 clients that will connect to the IIS or just five.

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Next Steps

Going forward, the CIR will continue to connect more health care providers to the Web Service, while continuing to push for more bi-directional communication in EHR vendor integrations. By August of this year, the CIR expects to have 200 facilities interoperable, with an additional 300 facilities interoperable by the end of 2012. As more facilities connect, the CIR will continue to monitor increases in the timeliness and completeness of reporting, as well as increases in provider and population up-to-date immunization coverage rates.

An important project involves the New York City public school system--the largest school system in the country, serving more than 1.1 million students. The schools currently use Automate the Schools (ATS), a mainframe-based administrative system, which has its own implementation of the immunization module, and is developing the capability to query the CIR’s Web Service for student immunization histories in order to import those histories into ATS. This will allow the school system to more efficiently verify compliance with immunization requirements. The completion of this project is expected to lead to enormous time savings for school personnel that currently manually enter each child’s immunization history into ATS. The school system will also benefit from receiving CIR decision support information, so that they no longer need to program and their decision support software for determining up-to-date status of students. Future enhancements to CIR services and networks include expanding the Web Service to support HL7 2.5.1 standards, and implementing a national standard Web Service interface for bi-directional HL7 communication.

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  1. Immunization Information System Annual Report, 2009. Submitted May 2010.
  2. Implementation Guide for Immunization Data Transactionspdf version [1.6 MB, 147 pages]
  3. CIR HL7 Web Service Integration Guide for Immunization TransactionsExternal Web Site Policypdf version [715 KB, 134 pages]
  4. Integrating Electronic Information to Improve Documentation of Immunization Rates for a Low-Income, Minority Population

See SOAP Web Services for additional implementation resources.

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