Vaccine Administration and Coverage by Jurisdiction (IIS), United States

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  • Influenza (flu) vaccination coverage for children and adults is assessed through U.S. jurisdictions’ Immunization Information Systems (IIS) data, submitted from jurisdictions to CDC monthly, in aggregate, by age group.
  • Influenza vaccination coverage estimate numerators include the number of people receiving at least one dose of influenza vaccine in a given flu season, based on information that state, territorial, and local public health agencies report to CDC. Some jurisdictions may report data submitted by tribes. Estimates include persons who are deceased but received a vaccination during the current season. People receiving doses are attributed to the jurisdiction in which the person resides unless noted otherwise. Quality and completeness of data may vary across jurisdictions. Influenza vaccination coverage denominators are obtained from 2020 U.S. Census Bureau population estimates.
  • Monthly estimates shown are cumulative, reflecting all persons vaccinated from July through a given month of that flu season. Cumulative estimates include any historical data reported since the previous submission. National estimates are not presented since not all U.S. jurisdictions are currently reporting their IIS data to CDC. Jurisdictions reporting data to CDC include U.S. states, some localities, and territories.
  • Because IIS data are intended to capture all vaccinations administered within a jurisdiction rather than a sample, standard errors were not calculated and statistical testing for differences in estimates across years were not performed.
  • Laws and policies regarding the submission of vaccination data to an IIS vary by state, which may impact the completeness of vaccination coverage reflected for a jurisdiction.
  • Coverage estimates based on IIS data are expected to differ from National Immunization Survey (NIS) estimates for children and adults. NIS estimates are based on a sample that may not be representative after survey weighting and vaccination status is determined by survey respondent rather than vaccine records or administrations. Quality and completeness of IIS data may vary across jurisdictions. In general, NIS estimates tend to overestimate coverage due to overreporting and IIS estimates may underestimate coverage due to incompleteness of data in certain jurisdictions.
  • IIS coverage estimates reported on jurisdictions’ dashboards may use different criteria for numerators and denominators (e.g. jurisdictions may use IIS-based denominator instead of census population) and thus may differ from those reported on CDC’s Weekly Flu Vaccination dashboard.
  • Figure 5A. Monthly Cumulative Number and Percent of Children 6 Months–17 Years Who Received 1+ Influenza Vaccination Doses*^, by Flu Season, Age Group, and Jurisdiction, United States. Data Source: Jurisdictional Immunization Information Systems (IIS). Data are current through February 29, 2024.
  • Figure 5B. Monthly Cumulative Number and Percent of Children 6 Months–17 Years Who Received 1+ Influenza Vaccination Doses and Comparison between 2023-2024 and Two Previous Seasons*^, by Age Group and Jurisdiction, United States. Data Source: Jurisdictional Immunization Information Systems (IIS). Data are current through February 29, 2024.
  • Figure 5C. Monthly Cumulative Number and Percent of Adults 18 Years and Older Who Received 1+ Influenza Vaccination Doses*^, by Flu Season, Age Group, and Jurisdiction, United States. Data Source: Jurisdictional Immunization Information Systems (IIS). Data are current through February 29, 2024.
  • Figure 5D. Monthly Cumulative Number and Percent of Adults 18 Years and Older Who Received 1+ Influenza Vaccination Doses and Comparison between 2023-2024 and Two Previous Seasons*^, by Age Group and Jurisdiction, United States. Data Source: Jurisdictional Immunization Information Systems (IIS). Data are current through February 29, 2024.
View & Download Data for Figs. 5B & 5D View & Download Data for Figs. 5A & 5C

*Some jurisdictions’ data are not displayed if they were not available by data retrieval timelines. These data include both valid and invalid doses, persons with last known addresses in the jurisdiction, and persons with unknown addresses within the jurisdiction. Data exclude persons whom a provider has indicated have left the jurisdiction. A period in time assessment is used to calculate influenza coverage, which is the preferred method when the period of eligibility of the vaccine is limited, as in the case for influenza season. This method requires for all individuals to be at least 6 months old by October 1st of the respective season to ensure that all individuals have an equal opportunity for vaccination during the designated vaccination period. Number of doses administered, and coverage estimates for a given month during the 2023-24 season may change over time for some jurisdictions. New York City (New York) and Philadelphia (Pennsylvania) report data separately from their respective states. New York state data exclude New York City and Pennsylvania state data exclude Philadelphia County. Coverage estimates for Wisconsin during the 2021-2022 and 2022-2023 seasons may be underestimated due to the inclusion of children 6-23 months as of July 1. Data updates are in progress to address this; in the meanwhile, the prior seasons’ estimates are not comparable to the 2023-2024 season (which includes children 6-23 months as of October 1). Chicago’s population was inadvertently omitted from Illinois’ population estimate in previous releases; on 3/9/24, this error was addressed and resulted in decreases in Illinois’ coverage estimates.

^ Figures 5A and 5C (line graphs) will not display any lines for jurisdictions whose data have not been submitted to CDC; these jurisdictions appear gray in the Figures 5B and 5D. Some Pacific Island jurisdictions’ vaccination programs may be aligned to regional virus circulation patterns (i.e., they may vaccinate on a different schedule than the continental U.S.).