Editor’s note: This investigation of NBC News 2026 data is an update of The vaccine divideoriginally published in September 2025. THE methodology for both projects is similar. The new data was collected from June to October 2026.
For “The Vaccine Divide,” NBC News gathered massive amounts of data from state governments and public records archives. With the help of infectious disease researchers at Stanford University, NBC News filed numerous document requests, including documents obtained under the Freedom of Information Act, and gathered different types of data in a standardized format to map and compare rates in thousands of countries.
Methodology
How NBC News collected the data
NBC News built a database of childhood vaccination information and exemptions using data provided by state governments, primarily health agencies. The data combines publicly available information for select states and data provided directly to NBC News.
The data covers vaccinations of kindergarten children for each school year.
After collection, the data was gathered and the exemption rates were calculated for analysis. The analysis focuses on four facets of the data:
- Medical Exemptions: Exemptions granted when students have health conditions that could make vaccination harmful.
- Non-Medical Exemptions: Exemptions for students who refuse required vaccinations due to personal or religious beliefs.
- MMR (measles-mumps-rubella) vaccinations: For states where data is subdivided by number of doses, MMR vaccination is counted by the second dose. Some states track measles, mumps, and rubella vaccinations separately; in these states, measles was used to represent MMR rates.
- Up-to-date immunizations: Students are considered “up-to-date” on their immunizations if they have received the full series of immunizations required for enrollment in their school.
How the data was processed
With a mix of formats, jurisdictions and collection practices across states, the task required extensive work to ensure potential inconsistencies in the data were managed.
- Some states, such as Ohio and New York, required additional calculations to aggregate state-provided data.
- Other states required manual entry of hundreds of rows of tabular data.
- All data has been verified for accuracy.
Analyze the data
This analysis of MMR vaccination rates among children focused on states that provided MMR numbers for the 2025-2026 school year. The analysis was accompanied by several variant analyses, which confirmed that the results were robust. The variant analyzes all yielded similar results, mostly within 1 percentage point. We also looked at how much the MMR vaccination rate has declined across all counties, with nearly 4 in 10 counties declining by more than 5 percentage points since 2019 and about 1 in 8 counties declining by that amount since 2024. Fewer than 2% of counties have declined by 0.1 percentage points or less since 2019.
Variations in data
Many states collect and report their data differently. Some use health districts rather than counties. Some states provided more than a decade of data; others only provided two years. Some states have deleted some data for privacy reasons.
- Not all states have recent data. Florida has not provided data on exemptions for kindergarten after the 2021-2022 school year. Montana stopped collecting data on vaccines and exemptions after 2019, first because of Covid and then because of the passage of a state bill (HB 334) in 2021 that overturned the state’s mandate to collect data on vaccinations.
- Some states (such as Arizona and Minnesota) do not collect “up-to-date” aggregate numbers representing the percentage of kindergartners who are compliant with all required vaccinations. Others (like Florida, New Hampshire, and South Carolina) only provided “up-to-date” numbers.
- In other states – Mississippi, New Hampshire and South Carolina – data was only provided for grades K-12, rather than specifically for kindergartners. West Virginia also falls into this category for its exemption data. Some states – Illinois and New York – do not collect data at the grade level, so the data is for elementary schools as a whole (through K-8 for Illinois, and New York was based on the count, with elementary schools defined as having less than 3% enrollment above grades K-6), rather than kindergartens specifically. Hawaii also falls into this category (through kindergarten and 5th grade), because its grade-level data was more consistent than its kindergarten-specific data.
- Other states did not provide county-level data. Alaska and Nebraska provided data for other jurisdictions. Delaware and Rhode Island were unable to provide county-level data; State-level figures were used instead. Indiana was unable to provide data on county-level exemptions. West Virginia was unable to provide county-level vaccination data, but IGT was able to provide county-level exemption data as of January 2025.
- Some states (like Michigan) collect data by calendar year rather than by school year.
- Wyoming did not consistently report data among kindergartners, so the most consistent reported value was used instead: one MMR dose among children 19 to 35 months of age. As a result, exemptions in children under 5 years of age were used to match this age group.
- Alaska was unable to provide data on regional exemptions due to confidentiality concerns due to small sample sizes.
Gn Health
