Trends in County-Level Childhood Vaccination Exemptions in the US

Abstract

This study examines US county-level trends in nonmedical and medical exemptions to childhood vaccination requirements.

US childhood vaccination rates are declining, posing the risk that vaccine-preventable infectious diseases will resurge.^1,2 Nonmedical exemptions to school-based childhood vaccination requirements are associated with lower vaccination coverage and increased risk of outbreaks, and the American Academy of Pediatrics has advocated that states eliminate such exemptions.^3,4,5 Although vaccination data are often tracked at the state level, county-level data are more relevant to population immunity and infectious disease risk.^1,6 The objective of this study was to describe US county-level trends in nonmedical and medical exemptions to childhood vaccination requirements.

Methods

We obtained county-level data on nonmedical and medical exemptions to childhood vaccination requirements (defined as exemption from any vaccine, except as noted in Supplement 2) from 2010 to 2024, predominantly for entering kindergarteners. Nonmedical exemptions included those granted for personal belief or religious reasons. Data were obtained by sending data requests to all 50 US states and the District of Columbia or using publicly available data. Most states reported county-level percentages of students with a vaccine exemption. Supplement 2 provides a detailed description of the dataset for each state, including outcome measure, years of data, age group, data processing steps, and relevant data notes. Statistically significant temporal trends were assessed using quantile regression (Supplement 1). The Stanford University Institutional Review Board deemed this project not human subjects research. Analytic code (R version 4.4.2 [R Foundation]) and data are available (Supplement 3). Analyses were 2 sided, and significance is defined in Supplement 1. We followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guideline.

Results

Vaccine exemption data from 3053 counties (or substate administrative units, eg, school districts, parishes, health department jurisdictions) across 45 US states and the District of Columbia were analyzed, of which 91.1% included at least 5 years of data and 98.0% included at least 1 year of data from 2021 to 2024. The median (IQR) county-level nonmedical exemption rate increased from 0.6% (0.0%-1.6%) in 2010-2011 to 3.1% (1.3%-5.8%) in 2023-2024, while medical exemptions remained stable (Figure 1). The median nonmedical exemption rate increased by 0.11 (95% CI, 0.10-0.12) percentage points annually from 2010 to 2020 and by 0.52 (95% CI, 0.48-0.57) percentage points annually from 2021 to 2024. Substantial variation was observed in county-level nonmedical exemption rates over 2 periods and in county-level variation by state (Figure 2). From 2021 to 2024, compared with 2010 to 2020, 53.5% of the 2842 counties included in the study with data available over both periods reported an increase in nonmedical exemptions greater than 1%, and 5.3% of counties reported an increase greater than 5%. Utah, Idaho, Oregon, Wisconsin, and Arizona had the highest rates of nonmedical exemptions from 2021 to 2024. States that eliminated nonmedical exemptions during this period (California, Connecticut, Maine, New York) had declines.

Figure 1. Temporal Trends in County-Level Nonmedical and Medical Vaccine Exemptions in the US.

Estimated median annual county-level nonmedical and medical exemption rates to childhood vaccination requirements over the study period. The line represents the median, the dark shading represents the IQR, and the light shading represents the middle 95th percentile. Data reporting varied by state in terms of definition and availability of vaccine exemptions, reporting systems, and other data factors (Supplement 2). The availability of county-level data generally increased over the study period, and therefore the number of counties (or substate administrative units) was included over time. Increasing nonmedical exemptions were observed (annual median rate of rise increased during the 2021-2024 postpandemic period, see eAppendix in Supplement 1), while medical exemptions remained stable over time. States with only state-level data and suppressed counties were excluded.

Figure 2. Spatial and Temporal Trends in County-Level Nonmedical Exemptions .

A, Data reporting varied by state in terms of definition and availability of nonmedical exemptions, reporting systems, and other data factors (see eAppendix in Supplement 1). B, Boxes indicate the middle 50% of values, the horizontal line inside the box represents the median estimate, the dots represent outliers, and error bars indicate 95% CIs. The prepandemic period included 2020 given timing of childhood vaccine receipt may precede their entry into kindergarten. A trend toward increasing nonmedical exemptions was observed in the postpandemic period. States with only state-level data, states with few counties (<5), and suppressed counties were excluded. NA indicates not available.

Discussion

This study identified an increase in nonmedical exemptions to childhood vaccination requirements from 2010 to 2024, with wide variation among counties and states and an increase following the COVID-19 pandemic, which may contribute to resurgence of vaccine-preventable diseases. This county-level analysis reveals geographically focused areas of high vaccine exemptions that are less evident at the state level. Continuation of these increases in nonmedical exemptions could contribute to declining vaccination and resurgence of vaccine-preventable infectious diseases in the US.^1,2 These findings support the need to reconsider policy on use of nonmedical exemptions, which are actively being debated, to address declining childhood vaccination in the US.^1,2

This analysis has limitations. The dataset did not cover all US counties over the entire study period, although most US counties contributed at least 1 year of data. Data were obtained from state public health and education departments, and their accuracy was not independently verified. States vary in their vaccine requirements, exemption policies, exemption definitions (any vaccine or measles, mumps, and rubella vaccine alone), data collection and reporting, and methods of estimating exemption rates. Nonmedical exemption estimates did not distinguish between personal belief vs religious exemptions. These estimates primarily reflect children in public schools, and often private schools; home-schooled children (who may have lower rates of vaccination) are often excluded.

This study found increasing nonmedical vaccine exemptions, most concentrated in a fraction of US counties, which may contribute to resurgence of vaccine-preventable diseases.

Supplement 1.

eAppendix 1. Additional methods

Supplement 2.

eTable. Description of data

Supplement 3.

Data sharing statement