About Immunization Data

The Iowa Immunization Program uses data from the Immunization Registry Information System (IRIS) to calculate county and state immunization rates for specific populations, including 2-year-old children and adolescents, and for specific vaccines, including HPV and influenza. The Program uses school and child care audit assessment data to ensure attendees receive the required immunizations.

This page provides general information about immunization data and measures developed by the Iowa Public Health Tracking program. Contact Us for more information about these data.

Information on this page:

How can we use this data?

  • Immunization and assessment data give Iowa health care providers and state and local partners valuable data to track progress toward goals, improve immunization practices, and guide strategies to improve immunization service delivery and policies.
  • Immunization data may identify pockets of need, unimmunized or underimmunized populations that present an increased disease risk.

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What are the sources of the data?

  • Iowa’s Immunization Registry Information System (IRIS) is a confidential, computerized repository of individual immunization records from participating public and private health care providers. IRIS includes patient records from all ages and is used to keep patients on schedule for recommended immunizations by storing immunization records, validating immunization history, providing vaccine recommendations, producing patient reminder and recall notices.
  • School and Child care audits: Annually, Local Public Health Agencies (LPHAs) assess immunization records of students enrolled in licensed child care centers and public, private and parochial students in kindergarten through 12th grade. Assessments are conducted to ensure attendees receive the required immunizations.

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What do these data tell us?

  • The vaccine coverage by antigen or series in Iowa residents.
  • If a measure is increasing or decreasing over time.

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What can these data not tell us and what are some limitations?

  • The quality of data in IRIS and the calculated coverage rates are dependent upon health care provider participation in the registry, management of records for individuals who have moved, died, or gone elsewhere, and collection of information on doses administered prior to the launch of IRIS in 2001.
  • IRIS does not routinely receive immunization data from other states and the Program does not maintain paper copies of immunization records. A resident can ask healthcare providers to have immunization information entered into IRIS. These limitations may affect the vaccine coverage in counties that border other states and among patients that received vaccines prior to 2001.
  • The data may include individuals that no longer reside in Iowa, but still have an active record in IRIS. These records may affect the overall immunization rate.
  • Influenza data is updated weekly and is based upon doses of vaccine reported to IRIS. The percent of population vaccinated includes the assumption of one dose of vaccine equates to one person vaccinated during the time period.
  • School and childcare audit data do not provide a full picture of all children’s immunization history. Vaccination and exemption status reflects the child's status at the time of assessment. Some children may be in the process of receiving required vaccines and final vaccination or exemption status may change after completion of the audit. In addition, some students with exemptions may have received some of the required vaccines.

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What time period of data is available?

  • The Iowa Public Health Tracking portal displays childhood and adolescent immunization data from 2011 through the most recent available data.
  • The influenza vaccine data is available from the 2016-17 flu season through the most recent available data. The influenza data will be updated weekly from August to May.

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What calculations are presented in the Tracking Portal?

  • Rate of Immunization by IRIS population or Percent Immunized: Calculated by dividing the number of immunized individuals (numerator) by the population in the selected age group and/or geographic area in IRIS (denominator).
  • Rate of Immunization by Census Population: The Number of Immunized Patients divided by the population of the same-aged population and geographic area.
  • Census Population with IRIS Record: The percent of the Census population with patient record in IRIS, calculated as the number of patient records in IRIS divided by the county Census population. This measure demonstrates the completeness of IRIS data and representation of the county population in IRIS.

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How are rates calculated?

The Portal provides immunization rates based on different population denominators, the number of patient records in IRIS and census estimates.

  • IRIS - A benefit of using rates calculated with the number of patient records in IRIS is the numerator is contained in the denominator. This method provides a better understanding of the immunization rate for the active population. However, these rates may include individuals that have moved out of the county or state.
  • Census - A benefit of using rates calculated with Census estimates is the ability to understand the county immunization rate for all individuals regardless if there is a patient record in IRIS. This information allows a susceptible population to be determined. However, census data is an estimate and may not include a true representation of the population resulting either in an over or under estimation. 

The American Immunization Registry Association’s Analytic Guide for Assessing Vaccination Coverage Using an Immunization Information System provides more information about selecting the denominator.

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What is the difference between childhood/adolescent immunizations and school assessment data?

Immunization data for children and adolescents is different from data presented in school audits due to evaluating different vaccine series and at different ages. Immunization data for 2 year-old children evaluates if children received recommended vaccines on schedule by age 24 months. Immunization data for adolescents evaluates if children received recommended vaccines on schedule. School and child care audit data assesses compliance with Iowa Code, Chapter 139a.8(6) and Iowa Administrative Code, 641-7.7(139). Additionally, child care audits may include children as young as 4 months and older than 24 months, while children included in the 2 year-old data may not attend child care and would not be included in the audit.

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Where can I find more technical information about the data?

Contact Us to learn more about Immunization data, or any of the measures displayed on the Iowa Public Health Tracking Portal.

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