Facebook Pages, the "Disneyland" Measles Outbreak, and Promotion of Vaccine Refusal as a Civil Right, 2009-2019.

Abstract

<i>Objectives.</i> To understand changes in how Facebook pages frame vaccine opposition.<i>Methods.</i> We categorized 204 Facebook pages expressing vaccine opposition, extracting public posts through November 20, 2019. We analyzed posts from October 2009 through October 2019 to examine if pages' content was coalescing.<i>Results.</i> Activity in pages promoting vaccine choice as a civil liberty increased in January 2015, April 2016, and January 2019 (<i>t</i>[76] = 11.33 [<i>P</i> < .001]; <i>t</i>[46] = 7.88 [<i>P</i> < .001]; and <i>t</i>[41] = 17.27 [<i>P</i> < .001], respectively). The 2019 increase was strongest in pages mentioning US states (<i>t</i>[41] = 19.06; <i>P</i> < .001). Discussion about vaccine safety decreased (<i>r</i>_<i>s</i>[119] = -0.61; <i>P</i> < .001) while discussion about civil liberties increased (<i>r</i>_<i>s</i>[119] = 0.33; <i>Py</i> < .001]). Page categories increasingly resembled one another (civil liberties: <i>r</i>_<i>s</i>[119] = -0.50 [<i>P</i> < .001]; alternative medicine: <i>r</i>_<i>s</i>[84] = -0.77 [<i>P</i> < .001]; conspiracy theories: <i>r</i>_<i>s</i>[119] = -0.46 [<i>P</i> < .001]; morality: <i>r</i>_<i>s</i>[106] = -0.65 [<i>P</i> < .001]; safety and efficacy: <i>r</i>_<i>s</i>[119] = -0.46 [<i>P</i> < .001]).<i>Conclusions.</i> The "Disneyland" measles outbreak drew vaccine opposition into the political mainstream, followed by promotional campaigns conducted in pages framing vaccine refusal as a civil right. Political mobilization in state-focused pages followed in 2019.<i>Public Health Implications.</i> Policymakers should expect increasing attempts to alter state legislation associated with vaccine exemptions, potentially accompanied by fiercer lobbying from specific celebrities.