pediatric ehr

PCC Unveils "Cool" New Imms Forecasting Vendor

PCC is located in the heart of New England, so we’re not strangers to snow and chilly weather, and we’re not afraid of a little ICE… especially when ICE is short for the Immunization Calculation Engine (ICE), a public health open-source solution developed and managed by HLN Consulting. The ICE service launched in PCC EHR in October 2023 and PCC users are already impressed with the speed of its updates, which follow the CDC’s vaccine rules. Keep reading for a look at how ICE came to be and how its open-source nature makes it a great fit for PCC practices.

From ACIP to Z: How Vaccine Recommendations Are Made

The Immunization Calculation Engine (ICE) is an immunization forecaster developed by HLN Consulting. The service includes vaccine schedule recommendations and vaccine forecasting in accordance with the Centers for Disease Control and Prevention’s (CDC’s) latest vaccination recommendations. 

That’s a lot of acronyms! What does ICE have to do with PCC EHR and my practice’s immunization forecasting?

Great question! Here’s how the process works: when a new vaccine is created by a manufacturer, it goes through an approval process with the Food & Drug Administration (FDA). 



Once the vaccine is approved, clinical guidelines, including recommended timing, dosage, and other clinical factors, are determined by ACIP, the Advisory Committee on Immunization Practices, a Federal advisory committee to the CDC, and approved by the CDC director. 

ACIP/the CDC publishes vaccine recommendations using clinical language in journals such as “The Pink Book” and the Morbidity and Mortality Weekly Report (MMWR)

Subject matter experts then take these recommendations and interpret them into languages that health information systems (HIS), electronic health records (EHRs), and immunization information systems (IIS) can understand. These experts are assisted by the CDC’s CDSi project, which “develop[s] and maintains resources to aid HIS implementers align with the current ACIP recommendations.”

This is how vaccine recommendations come to ICE, developed by HLN. 

ICE began as a project by the New York City immunization registry. In 2010, the New York City health officials became dissatisfied with the maintainability of the current ICE product. They asked HLN Consulting to develop a third iteration of the service and to maintain its support and development, with one big caveat: that the service remains open-source and that future iterations of the product would be shared publicly.

This has resulted in the ICE service available today.

About ICE & PCC


HLN Consulting founder Noam Arzt, PhD described the state of interpreting clinical guidelines into programming language prior to ICE like this:

“Invariably, these systems become unsupportable spaghetti code with increasing reliance on the one or maybe two programmers who made a significant investment of their time in learning the background, complex structure, and functionality of the system. And testing these systems has always been challenging due to their complex nature and the interconnectedness of some of the rules.”

ICE, then, provides the shell in which new vaccine rules are placed and tested against what the data already knows. In developing ICE, Dr. Arzt said that clarity and transparency are keys to making ICE the service that best serves developers and providers. “We wanted to be as transparent as possible. We publish as we go.”

This commitment to transparency and ICE’s open-source nature was a perfect fit for PCC EHR. PCC chose ICE as our new immunization forecasting vendor and went live with the software in late 2023. The results were immediate: developer Brian LaClair noted that the data is more accurate and processes are 73% faster than before.

"Our transition to HLN's ICE provides PCC's clients with a faster, significantly more accurate, and more robust vaccine forecasting solution,” says LaClair. “This service not only operates faster, but also receives quicker and more rigorously tested updates. With ICE, PCC is able to fully test new vaccine rule sets before they are released to clients to ensure accuracy. In the future, ICE will enable PCC to use other factors from each patients chart to provide even more accuracy in any scenario."

Pediatricians approve of the change, too: Dr. Seth Kaplan of TLC Pediatrics remarked that the new registry is more accurate and works well, while Topeka Pediatrics said, “We don’t notice the refresh time. It’s a big improvement!”

ICE vigorously tests new rules before publication: over 3750 test cases! This has made HLN’s documentation celebrated in the field and cross-referenced by other SMEs. In addition, PCC uses over 1000 test scenarios to ensure all recommendations appear just as they should be in the EHR.

What does this mean for PCC EHR users? A faster, more accurate, and trustworthy immunization evaluation and forecasting system, tested vigorously by both HLN Consulting and PCC. Plus, there’s more to look forward to since ICE is open source, PCC can make its own changes to ICE, which benefits not only PCC EHR users but everyone using ICE for the improvement of vaccine information.

About HLN

HLN is a leading health informatics consulting company providing software development and technical support services to immunization information systems (IIS) as well as other health systems since 1997. HLN is focused on leveraging an open source collaborative development model as the most efficient and cost-effective way to build and support robust technical solutions that address pressing public health needs. 

HLN maintains the Immunization Calculation Engine (ICE), an open-source immunization forecasting evaluation and software system. The default ICE immunization schedule supports all routine childhood, adolescent, and adult immunizations in the United States. It is based on the recommendations of the Advisory Committee on Immunization Practices (ACIP). 

Noam Arzt, President of HLN Consulting stated “HLN is thrilled to partner with PCC to support their client’s use of ICE for immunization clinical decision support at the point of care.”

More information on HLN Consulting and its open source products can be found at

Allie Squires

Allie Squires is PCC's Marketing Content Writer and editor of The Independent Pediatrician. She holds a master's in Professional Writing from NYU.