(iPoster) Why Brazilians Stop Vaccinating: Trust, Misinformation, and Political Cues

• In Event: Poster Sessions: Health Politics and Policy & Wartime Violence, Armed Actors, and Civilian Agency
  In Poster Session: Poster Session: Health Politics and Policy

Abstract

How do political cues, institutional trust, and misinformation shape individual compliance with public health interventions? After decades of near-universal coverage, vaccination rates in Brazil have declined since 2015, placing around 85% of municipalities at high risk for measles outbreaks. This decline is puzzling because it is territorially uneven and began before both Bolsonaro’s vaccine-skeptic administration and the COVID-19 pandemic, the two most common explanations. This paper examines changes in vaccination uptake using a mixed-methods design that combines a survey experiment, large-language-model processing of anti-vaccine Telegram groups, and 122 in-depth interviews conducted between 2022 and 2025. I argue that public opinion has shifted and this paper identifies three individual-level factors that shape vaccine uptake, both independently and interactively: (1) institutional distrust, (2) belief in misinformation, and (3) co-partisanship with anti-vaccine leaders. Trust in (sub)national health authorities and rejection of false claims that undermine vaccine confidence are associated with higher uptake. However, these effects interact: the positive impact of institutional trust is weakened -- or even reversed -- among individuals who are co-partisans of anti-vaccine leaders and who believe in misinformation. Likewise, the negative effect of misinformation is strongest among co-partisans of anti-vaccine political elites.

Author

• Unregistered Participant