Trends and Characteristics of Proposed and Enacted State Legislation on Childhood Vaccination Exemption, 2011-2017.

To examine trends and characteristics of proposed and enacted state legislation that would directly affect states' immunization exemption laws. We performed content analysis of proposed bills in state legislatures from 2011 to 2017. We classified bills as provaccination or antivaccination. State legislators proposed 175 bills, with the volume increasing over time: 92 (53%) bills expanded access to exemptions, and 83 (47%) limited the ability to exempt. Of the 13 bills signed into law, 12 (92%) limited the ability to exempt. Bills that expanded access to exemptions were more likely to come from Republican legislators and Northeastern and Southern states. Although most proposed legislation would have expanded access to exemptions, bills that limited exemptions were more likely to be enacted into law. Legal barriers to exempt one's children from vaccination persist despite vaccine hesitancy, which is encouraging for public health. Most vaccine exemption laws introduced in state legislatures would pose threats to the public's health. There is a need for constituents to engage their elected legislators and advocate provaccination policies.