Association of Vaccine-Preventable Disease Incidence With Proposed State Vaccine Exemption Legislation

The frequency of vaccine-preventable disease (VPD) outbreaks is increasing in the United States. A principal factor in disease transmission has been susceptible, nonimmune children whose parents have opted to exempt them from school-entry vaccination requirements.¹ Prior research has shown a concerning increase in the volume of state legislation introduced to expand exemptions.²

In 2018, a temporal link between disease outbreaks and vaccination uptake was described, whereby an increase in reported cases of pertussis subsequently motivated receipt of pertussis vaccination.³ Similar dynamics may be present in legislation, whereby increases in reported VPDs may prompt a legislative response. Thus, we sought to assess whether state trends in VPDs were associated with trends in the introduction of state legislation that would alter vaccine exemption laws.

We linked state VPDs reported to the National Notifiable Diseases Surveillance System (NNDSS)⁴ to an existing data set of proposed bills that would impact state vaccination exemption laws between 2011 and 2017. Because these data were publicly available deidentified state-level aggregates, institutional review board approval and informed consent were not required. We aggregated the reports for all states between 2010 and 2016, allowing for a 1-year lag to allow time for an uptick in disease to prompt a legislative response. We limited the NNDSS data to diphtheria; Haemophilus influenzae serotype B; hepatitis A and B; influenza; pneumococcal disease; measles; meningococcal disease serotypes A, B, C, Y, and W-135; mumps; pertussis; rubella and congenital rubella syndrome; tetanus; and varicella. These VPDs were selected based on the Advisory Committee on Immunization Practices childhood schedule.⁵

We correlated VPDs (independent variable, operationalized per 100 000 population and standardized as z scores) with subsequent legislative activity operationalized as counts of bills that expanded or restricted the ability to exempt from school-entry vaccine requirements (dependent variables; bill classification details published elsewhere²). Poisson mixed-effects regression models were used to account for within-state correlations and control for secular trends; an offset term was specified as the log of each state’s population size. Analyses were stratified by proposed bills that would (1) expand vaccine exemptions and (2) restrict vaccine exemptions. A sensitivity analysis restricted the independent variable to pertussis, which was selected because pertussis outbreaks have garnered widespread attention and thus may prompt legislative action. Data set and code are available at https://doi.org/10.5281/zenodo.3241849.

On average, each state reported a mean (SD) of 25 (17) VPDs per 100 000 people per year (Table 1). There were 175 vaccine exemption-related bills proposed, of which 92 (53%) expanded exemptions and 83 (47%) restricted exemptions.² In the analysis limited to bills that would restrict exemptions, each SD increase in VPDs per 100 000 people was associated with with 54% more bills being proposed (95% CI, 27%-88%), controlling for year-to-year differences. In the analysis limited to bills that would expand exemptions, reported VPDs were not statistically associated with bill proposals. However, when restricting VPDs to only pertussis, the sensitivity analysis revealed significant associations with both types of bills (Table 2).

This study revealed an association between reported VPDs and proposed state legislation that would alter vaccine exemption law. Specifically, increased VPDs were associated with an increase in bills that would restrict vaccine exemptions. A potential explanation of this association is that an uptick in VPDs prompts media coverage, raises public awareness, and increases advocacy and subsequent legislative response. This is supported by the sensitivity analysis results that were limited to a disease that has garnered substantial media attention (ie, pertussis).

Our work is predicated on the assumption that exemptions drive outbreaks. There may be other reasons, such as vaccine failure. A second limitation is that our data do not capture the 2019 measles outbreak. Indeed, this outbreak resulted in New York removing nonmedical school vaccination exemptions⁶ through the mechanisms we describe.

Counter to the conventional examination of how laws affect health,⁷ we flipped the model to explore how health is associated with legislative activity. Results suggest that state legislators may respond to actionable health concerns and introduce bills to decrease the use of nonmedical vaccine exemptions. This is promising in light of increasing vaccine hesitancy and misinformation about childhood vaccinations.

Corresponding Author: Neal D. Goldstein, PhD, MBI, Dornsife School of Public Health, Department of Epidemiology & Biostatistics, Drexel University, 3215 Market St, Philadelphia, PA 19104 (ng338@drexel.edu).

Accepted for Publication: June 28, 2019.

Published Online: November 18, 2019. doi:10.1001/jamapediatrics.2019.4365

Author Contributions: Dr Goldstein had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: All authors.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Goldstein, Suder.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Goldstein.

Administrative, technical, or material support: Suder.

Supervision: Goldstein, Suder.

Conflict of Interest Disclosures: Dr Goldstein consults for Merck Sharp & Dohme. No other disclosures were reported.

Disclaimer: The contents of this article are solely the responsibility of the authors and do not necessarily represent the official views of the Delaware Department of Justice.

Meeting Presentation: This a portion of this paper was presented at the 2019 Annual Meeting of the American Public Health Association; November 3, 2019; Philadelphia, Pennsylvania.