In an update to its 2025 investigation, NBC News released a detailed account of how it assembled a nationwide picture of kindergarten vaccination and exemption rates for the 2025‑26 school year. The data collection, which took place from June to October 2026, relied on public records from state health agencies and, where necessary, direct provision of data to the news organization. The effort was guided by infectious‑disease researchers at Stanford University, who helped shape requests for documents, including Freedom of Information Act submissions.
Data sources and scope
The resulting database captures information on kindergarten immunizations for each academic year, focusing on four key metrics: medical exemptions, non‑medical exemptions (religious or personal‑belief based), measles‑mumps‑rubella (MMR) vaccination status, and overall “up‑to‑date” vaccination compliance. For MMR, the second dose serves as the benchmark where states report it that way; in states that separate measles, mumps and rubella, measles figures are used as a proxy for the full MMR series.
Because states differ in how they collect and publish data, NBC News faced a patchwork of formats. Some jurisdictions, such as Ohio and New York, required additional calculations to aggregate the raw numbers supplied by the states. In other cases, researchers entered hundreds of rows of tabular data by hand. Every entry was cross‑checked for accuracy before being merged into the central repository.
Processing challenges and variations
The investigation notes that not all states provide recent or uniform data. Florida, for example, stopped reporting kindergarten exemption figures after the 2021‑22 school year, while Montana halted collection entirely after 2019, first due to the pandemic and later because a 2021 state bill (HB 334) eliminated the mandate to collect immunization data. Arizona and Minnesota do not publish overall “up‑to‑date” percentages for kindergarteners, whereas Florida, New Hampshire and South Carolina report only those figures.
Additional inconsistencies arise from the level of granularity. Mississippi, New Hampshire and South Carolina supplied data for K‑12 students rather than kindergarten‑specific numbers, and West Virginia followed the same pattern for exemption data. Illinois and New York aggregate data at the elementary‑school level (K‑8 for Illinois; headcounts for New York schools with less than 3 % enrollment above grades K‑6). Hawaii’s most consistent data set covers pre‑K‑5 rather than kindergarten alone.
Several states could not provide county‑level data. Alaska and Nebraska reported figures for broader jurisdictions, while Delaware, Rhode Island and Indiana lacked county‑level exemption numbers, forcing analysts to rely on state‑wide totals. West Virginia could not offer county immunization data but did supply county exemption data beginning in January 2025. Michigan reports by calendar year instead of school year, and Wyoming’s most reliable metric is one‑dose MMR among children aged 19‑35 months, which the team aligned with exemption data for children under five.
Key findings from the analysis
The primary analysis concentrated on states that supplied MMR figures for the 2025‑26 school year. Variant analyses—alternative calculations designed to test robustness—produced results that differed by no more than one percentage point, confirming the stability of the core findings.
Among the most striking observations, almost 40 % of counties experienced a decline of more than five percentage points in MMR vaccination rates since 2019. An additional one‑eighth of counties showed a similar drop since 2024. By contrast, fewer than two percent of counties recorded a change of 0.1 percentage points or less over the same period, indicating that the majority of jurisdictions are seeing measurable erosion in vaccine coverage.
These trends underscore the importance of consistent, high‑quality data collection across states. The methodological note stresses that while the database represents the most comprehensive effort to date, gaps—such as missing recent data from Florida or the cessation of reporting in Montana—limit the ability to draw a fully national picture. Nevertheless, the assembled data provides a crucial baseline for public‑health officials, policymakers and researchers monitoring childhood immunization rates across the United States.
Helene Elliott is the Lead Science & Space Reporter at News Raise. She reports on aerospace missions, astrophysics discoveries, quantum research, and environmental technology.
