Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
UPDATE
Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.
UPDATE
The White House announced that vaccines will be required for international travelers coming into the United States, with an effective date of November 8, 2021. For purposes of entry into the United States, vaccines accepted will include FDA approved or authorized and WHO Emergency Use Listing vaccines. More information is available here.
UPDATE
Travel requirements to enter the United States are changing, starting November 8, 2021. More information is available here.

Data Definitions for COVID-19 Vaccinations in the United States

Data Definitions for COVID-19 Vaccinations in the United States
Updated Feb. 2, 2023

COVID-19 Data Tracker

CDC reports COVID-19 vaccination data online on COVID Data Tracker and in vaccination datasets. Sharing timely and accurate information with the public is one of CDC’s core activities. Timely and accurate reporting from jurisdictions provides the reliable data that can be reported by CDC. All reported numbers may change over time as updated data are continuously reported to CDC.

How CDC Estimates Vaccination Coverage

CDC estimates the number of people receiving at least one dose, the number of people who are fully vaccinated, and the number of people with booster doses. CDC estimates are based on data that include a dose number (first, second, or booster). To protect the privacy of vaccine recipients, CDC receives data without any personally identifiable information (deidentified data). Each jurisdiction or provider uses a unique person identifier to link records within their own systems. However, CDC cannot use the unique person identifier to identify individual people by name.

There are challenges in linking records when someone receives vaccine doses in different jurisdictions or from different providers. That person could receive different unique person identifiers for different doses. CDC may not be able to link multiple unique person identifiers for different jurisdictions or providers to a single person, and subsequent doses may appear to be a first dose when reported. Thus, CDC’s data may over-estimate first doses and under-estimate subsequent doses.

Another issue that poses challenges to estimating doses administered is that different jurisdictions and providers use different reporting practices. As people receiving doses are attributed to the jurisdiction in which they reside, the reporting method might change between doses if they move to a different jurisdiction. Also, CDC may lack information about a person’s residence. These issues can cause CDC’s dose number estimates to differ from those reported by jurisdictions and federal entities.

CDC has capped estimates of vaccination coverage shown on COVID Data Tracker at 95%. This cap helps address potential over-estimates of vaccination coverage due to first, second, and booster doses that were not linked. Other reasons for overestimates include census denominator data not including part-time residents or potential data reporting errors. Previously, CDC had capped estimates of vaccination coverage at 99.9%. CDC changed the cap to 95% on December 9, 2021, to account for differences in the accuracy of vaccination coverage estimates between different jurisdictions.

CDC encourages people to bring their CDC COVID-19 Vaccination record card with them to their appointment for another COVID-19 vaccine dose because having the card will help ensure the doses are linked.

How CDC Attributes Doses

CDC determines the number of people receiving at least one dose, the number of people who are fully vaccinated, and the number of people with an updated (bivalent) booster dose based on information reported to CDC on dose number, dose manufacturer, administration date, recipient ID, and date of submission. Because the method used to determine dose numbers needs to be applied across multiple jurisdictions with different reporting practices, CDC’s dose number estimates might differ from those reported by jurisdictions and federal entities. People receiving doses are attributed to the jurisdiction in which they reside. This includes doses administered by Federal Emergency Management Agency (FEMA) partner sites, Health Resources and Services Administration (HRSA) partner sites, and federal entity facilities. In some limited circumstances, people might receive vaccinations outside the jurisdiction (state, territory, tribe, or local entity) where they live. When the vaccine manufacturer is not reported, the recipient is considered fully vaccinated with two doses.

COVID-19 Vaccinations Data Definitions

COVID-19 Vaccination Data Systems and Data Sources

CDC uses multiple information technology systems to rapidly collect reliable data about how many doses of COVID-19 vaccines have been distributed and how many people have been vaccinated with those doses (administration). CDC — together with other federal agencies, vaccine providers, jurisdictions, state/local public health departments, and tribal health facilities across the United States — uses these data systems to inform decision-making regarding COVID-19 vaccination. The COVID-19 Vaccination IT Overview provides an overarching view of the vaccine IT data systems and how they integrate to track COVID-19 vaccine distribution and administration.

Vaccine distribution data systems

System

System

System

Description

Description

Description

CDC’s vaccine order management system where jurisdictions (states, territories, tribes, and local entities), federal agencies, and pharmacy partners order vaccines from the federal government.

Description

CDC’s vaccine order management system where jurisdictions (states, territories, tribes, and local entities), federal agencies, and pharmacy partners order vaccines from the federal government.

CDC’s platform where federal entity providers report their on-hand COVID-19 vaccine inventory each day.

Description

CDC’s platform where federal entity providers report their on-hand COVID-19 vaccine inventory each day.

Immunization Data Lake (IZDL)

System

Immunization Data Lake (IZDL)

A cloud-hosted data repository to receive, store, manage, and analyze deidentified COVID-19 vaccination data.

Description

A cloud-hosted data repository to receive, store, manage, and analyze deidentified COVID-19 vaccination data.

Vaccine administration data systems

System

System

System

Description

Description

Description

Most IISs create a centralized data repository for storing vaccination information specific to that jurisdiction.

Description

Most IISs create a centralized data repository for storing vaccination information specific to that jurisdiction.

A web-based application available to support planning and execution for temporary, mobile, or satellite COVID-19 vaccination clinics. VAMS connects with IISs and sends data to IISs through the COVID-19 Data Clearing House.

Description

A web-based application available to support planning and execution for temporary, mobile, or satellite COVID-19 vaccination clinics. VAMS connects with IISs and sends data to IISs through the COVID-19 Data Clearing House.

COVID-19 Data Clearing House

System

COVID-19 Data Clearing House

A cloud-hosted data repository that receives, deduplicates, and deidentifies COVID-19 vaccination data, which are then used to populate the Immunization (IZ) Data Lake.

Description

A cloud-hosted data repository that receives, deduplicates, and deidentifies COVID-19 vaccination data, which are then used to populate the Immunization (IZ) Data Lake.

Immunization Data Lake (IZ Data Lake)

System

Immunization Data Lake (IZ Data Lake)

A cloud-hosted data repository to receive, store, manage, and analyze deidentified COVID-19 vaccination data.

Description

A cloud-hosted data repository to receive, store, manage, and analyze deidentified COVID-19 vaccination data.

COVID-19 vaccination data sources

Population data sources

Reporting conditions

Jurisdictions currently collect demographic data and report it to CDC. Not all states and territories report to CDC demographic data on vaccine recipients; the laws in each state or territory dictate whether the state can collect or report demographic data.

Frequently Asked Questions about COVID-19 Vaccination Data

CDC reports COVID-19 vaccination data online on COVID Data Tracker and in vaccination datasets. Sharing timely and accurate information with the public is one of CDC’s core activities. Timely and accurate reporting from jurisdictions provides the reliable data that can be reported by CDC. All reported numbers may change over time as updated data are continuously reported to CDC.

COVID-19 Vaccine Distribution and Tracking

Vaccine Data Reporting

Data Variations

CDC Publicly Available Data

Vaccination information

Historical Updates

CDC communicates events that affect vaccine data through footnotes on COVID Data Tracker (CDT). This section serves as an archive of footnotes for historical COVID-19 vaccine data updates.  Reported changes to COVID-19 vaccine data can occur for the following reasons:

  • Updates to COVID-19 vaccine policy and guidance/recommendations
  • Data changes outside scheduled Record Management events
  • Changes in reporting methods
  • Adjustments made due to errors (such as syncing errors)

Record Management

Jurisdictions continuously receive new and updated vaccination information from partners that may require updating and/or deleting older records to maintain current data accuracy. Occasionally, an organization will delete a record with data fields that cannot be updated and upload a replacement record with the correct information. As part of ongoing efforts to improve data quality and maintain accurate COVID-19 vaccination information, CDC has been working with states to remove duplicate or incorrect vaccination records and to add replacement records. These collaborative updates help to ensure CDC is publicly providing the best, most up-to-date data. This option became available for select entities on July 14, 2021 and was expanded to all entities starting August 9, 2021. Historical update and delete events for reporting entities and their impacts on vaccine data are reported below.