Behind the NBC News Investigation into Declining Childhood Vaccination Rates
NBC News utilized extensive public records and expert collaboration to track national vaccination trends.
1Investigative Methodology Overview
NBC News conducted a comprehensive data investigation to track childhood vaccination trends across the United States. This project, an update to the 2025 Vaccine Divide report, involved gathering massive datasets from state health agencies. The team collaborated with infectious disease researchers at Stanford University to ensure the scientific rigor of their findings.
2Data Collection Challenges
The research team filed numerous document requests, including those under the Freedom of Information Act, to obtain necessary records. Because states utilize varying collection practices and reporting formats, the team faced significant hurdles. They worked to standardize these disparate records into a unified format to allow for accurate mapping across thousands of counties.
3Scope of the Analysis
The investigation focused on kindergartner vaccination data for each academic year, specifically targeting MMR immunization rates. Researchers analyzed states that provided figures for the 2025-26 school year. By collating this information, they calculated exemption rates to identify broader public health trends and potential risks associated with declining coverage in local communities.
4Managing Data Inconsistencies
States report data differently, with some using health districts instead of counties and others providing only limited historical data. Privacy concerns led some jurisdictions to redact specific information, further complicating the analysis. To manage these inconsistencies, the team performed extensive data cleaning to ensure the final results remained robust and reliable.
5Robustness of Findings
To verify the accuracy of their conclusions, the researchers conducted several variant analyses alongside the primary study. These additional tests consistently yielded similar results, with variations mostly staying within one percentage point. This process confirmed that the observed decline in vaccination rates was a statistically significant trend rather than a reporting error.
6Significant Regional Declines
The data revealed a stark downward trend in MMR vaccination coverage across the country. Almost four in ten counties experienced a decline of over five percentage points since 2019. Additionally, about one in eight counties saw a similar five-point drop since 2024, highlighting an accelerating trend in vaccine hesitancy or access issues.
7Minimal Stability Observed
The investigation found that very few areas maintained stable vaccination rates during the study period. Fewer than two percent of counties saw a decline of 0.1 percentage points or less since 2019. This widespread reduction suggests that the drop in childhood immunizations is a pervasive issue affecting the vast majority of American counties.
8Public Health Implications
By mapping these vaccination gaps, the NBC News investigation provides a critical look at the erosion of herd immunity. The findings underscore the necessity of standardized public health reporting to monitor infectious disease risks. This data-driven approach serves as a vital tool for policymakers and health officials addressing the national immunization crisis.