Non-medical exemptions and state-level variation in kindergarten MMR vaccination coverage, United States, 2016–2024

Background High kindergarten vaccination coverage is essential to sustain herd immunity against measles and other vaccine-preventable diseases. In recent years, rising state-level non-medical exemption rates and pandemic-related disruptions have threatened this protection in the United States. Methods We analyzed 8 years of Centers for Disease Control and Prevention (CDC) kindergarten vaccination surveillance data (2016–2017 through 2023–2024) to assess national and state-level trends in vaccination coverage and exemption rates. Descriptive analyses and scatterplots were used to examine patterns across years. A cross-sectional state-level linear regression model using 2024–2025 data ( N = 39 jurisdictions) was used to quantify the association between exemption prevalence and MMR vaccination coverage. Results National MMR coverage declined from 96.0% in the 2018–2019 school year to 92.7% in 2023–2024, while exemption rates increased from 2.5% to 3.3%. Updated 2024–2025 national estimates indicate that coverage remained near 92.5% and exemption rates increased further to 3.6%. In a cross-sectional analysis of 2024–2025 data, each 1% increase in exemption prevalence was associated with an approximately 1.1 percentage-point decrease in MMR coverage ( p < 0.001), with exemption prevalence accounting for approximately two-thirds of observed variation in coverage. States permitting broad non-medical exemptions, including Idaho and Alaska, consistently reported coverage below the 95% herd immunity threshold, whereas states with more restrictive exemption policies maintained near-universal coverage. Conclusion Non-medical exemptions are strongly associated with state-level differences in kindergarten vaccination coverage in the United States. These findings suggest that exemption policies may play an important role in shaping population-level protection, although causal relationships cannot be established from this analysis.