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What is ICE?

The Immunization Calculation Engine (ICE) is a free, open-source immunization forecasting software system. The core component of ICE is the ICE Web Service, which evaluates a patient's immunization history and generates the appropriate immunization recommendations for the patient. The ICE Web Service runs in OpenCDS which is a third-party platform that may be used to build decision support services for any clinical domain.

ICE comes initially configured with a default immunization schedule that supports all routine childhood, adolescent, and adult immunizations - based on the recommendations of the Advisory Committee on Immunization Practices (ACIP).

The ICE software system has been developed and configured by a collaborative partnership of public health experts and information technology experts from the organizations listed below and has been released under a standard open-source license:

Due to its standards-based Web Service interface, its Java-based implementation, and its complete lack of dependence on any commercial software, ICE can be deployed in diverse technical environments and easily integrates with third party clinical systems such as Immunization Information Systems (IIS), Electronic Health Record Systems (EHR-S), and Health Information Exchanges (HIEs).

Clinical systems utilize the ICE Web Service by passing a Virtual Medical Record (vMR) to its Web Service which adheres to the Decision Support Service (DSS) standard. In response, ICE utilizes its immunization rules and the data in the vMR, such as the patient’s date of birth, gender, immunization history, and disease indicators, to evaluate and return the validity of each immunization in the patient’s history along with one or more evaluation reasons. It also returns a recommendation for each vaccine group along with one or more recommendation reasons. ICE’s Web Service architecture scales to support simultaneous real-time processing of many patients submitted by one or more systems. It can also service requests for multiple immunization schedules. For example, a single ICE deployment could enforce one immunization schedule utilized by an IIS, another immunization schedule used by multiple EHR-S, and a third immunization schedule utilized by a school health system.

Current News

  • February 1, 2022 - New Release of ICE - Version 1.34.1
    • A new release of ICE is available  -  Download the latest ICE release now.
    • Version 1.34.1 includes the following additions and updates. Please see the Release Notes for details.
      • COVID-19 Vaccine Group Updates:

        • Booster Dose Rules 
          • Updated booster dose recommended age to 12 years
          • Updated booster dose recommended interval to 5 months after completion of mRNA vaccine primary series. 
        • Additional Dose Rules 
          • Added support for additional dose for immunocompromised persons aged 5+
        • COVID-19 Vaccines Not Authorized by FDA Rules
          • Updated rules for Novavax (CVX 211) COVID-19 vaccine now that WHO has approved it for use under their EUL
          • Updated rules to accommodate the fact that patients who have not completed all recommended doses of a COVID-19 vaccine series not authorized by FDA, but approved by WHO, do not need to restart a primary vaccination series in the United States. 
    • As always, you can determine which version of ICE you are currently using by viewing the README.HISTORY file that is included with each zipfile distribution.
    • If you have any questions, comments or suggestions, please e-mail us at

  • ICE Plans for COVID-19 Implementation
    • HLN is actively monitoring all news and updates in regards to new and existing COVID-19 vaccines.  
    • Once a vaccine has been approved for use by FDA (either Expanded Access, EUA, or full licensure), ACIP will hold an emergency meeting and publish recommendations in a very quick timeframe (i.e. days). HLN intends to release a version of ICE that includes COVID-19 forecasting as early as possible after ACIP has published the guidelines. This initial release will contain COVID-19 logic known at the time of the release. As additional, actionable information on COVID-19 forecasting becomes available from official sources, HLN will continue to release additional versions of ICE, at appropriate times to reflect ongoing updates.
    • If you have any questions, comments or suggestions, please e-mail us at

  • The Importance of Upgrading After Each ICE Release
    • With each new release, we strongly recommend that all users and service providers update their running instances of ICE as soon as possible to the latest version. Each new release contains important forecaster business logic updates and bug fixes.

  • ICE Code Systems and Codes Now Available in Google Sheets
    • The ICE code systems and codes are now accessible in Google Sheets as an added convenience. These are the codes as those in the Implementation Guide. The codes will continue be updated in both the places.
    • The Google Sheet is available here.

  • Configuration Note
    • As of release 1.24.1, the ICE service is configured with the output_supplemental_text option in the properties file set to enabled by default.
    • As of release 1.16.1, the ICE service is configured by default to return the earliest and overdue dates in addition to the recommendation date. In prior releases, the default configuration was to return only the recommendation date for the forecast.
      • If your application has not been configured to display the earliest and/or overdue dates, we recommend turning this feature off by changing the output_earliest_and_overdue_dates value in the file to "N". Failure to do so may result in incorrect interpretation of the recommendation date. 
      • If you are interested in returning the earliest date or overdue date, please refer to the latest ICE Implementation Guide for details indicating precisely where each of the forecast dates – earliest, recommended, and overdue – are specified in the ICE output, and under what circumstances.

For more information, see the Full List of Archived News...

ICE Wins a 2017 Upshot Award from the National Vaccine Program Office (NVPO)

On June 6, 2017, HLN was awarded the 2017 Upshot Award for Excellence in Vaccine Supply, Access, and Use by the National Vaccine Program Office (NVPO) for its ICE Open Source Immunization Forecaster. In the letter of award, Dr. Jewel Mullen, Principal Deputy Assistant Secretary for Health commented that,

"HLN Consulting’s efforts on the Immunization Calculation Engine (ICE) are impressive. This powerful tool-including its open-source nature and seamless integration into clinical workflows-holds great promise for improving clinical decision-support and ultimately vaccination rates. Thank you for daring to innovate, collaborate, and lead in an area that is not only complex, but constantly evolving."

Mike Suralik, one of HLN’s project managers, was on hand to receive the award at the meeting of the National Vaccine Advisory Committee in Washington, DC. HLN is pleased to accept this award on behalf of the ICE project. While we have been the lead organization, we consider ICE to be a community effort of interested public health organizations, clinical users, and software developers. This project would not be a success without ongoing cooperation between these participants. ICE is an important product for the immunization community. It is collaboratively developed, maintained, and supported yet is freely available for use. We hope ICE can gain a broad acceptance not only here in the US but across the world.

Try Using ICE from Your Web browser

A simple application, called "ICE Client", has been created and made freely available so that anyone can submit sample patient data to the ICE Web Service and see the evaluations and recommendations that the ICE Web Service returns. Try ICE now from your web browser.