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Cited by 403Misinformation and Its ImpactsVaccine Coverage and HesitancySocial Media and Politics

Polarization of the vaccination debate on Facebook

Open access
Schmidt, Ana Lucía, Zollo, Fabiana, Scala, Antonio, Betsch, Cornelia, Quattrociocchi, Walter·2018·Vaccine
DOI 10.1016/j.vaccine.2018.05.040
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Abstract

Background Vaccine hesitancy has been recognized as a major global health threat. Having access to any type of information in social media has been suggested as a potential influence on the growth of anti-vaccination groups. Recent studies w.r.t. other topics than vaccination show that access to a wide amount of content through the Internet without intermediaries resolved into major segregation of the users in polarized groups. Users select information adhering to theirs system of beliefs and tend to ignore dissenting information.Objectives The goal was to assess whether users' attitudes are polarized on the topic of vaccination on Facebook and how this polarization develops over time.Methods We perform a thorough quantitative analysis by studying the interaction of 2.6 M users with 298,018 Facebook posts over a time span of seven years and 5 months. We applied community detection algorithms to automatically detect the emergence of communities accounting for the users' activity on the pages. Also, we quantified the cohesiveness of these communities over time.Results Our findings show that the consumption of content about vaccines is dominated by the echo chamber effect and that polarization increased over the years. Well-segregated communities emerge from the users' consumption habits i.e., the majority of users consume information in favor or against vaccines, not both.Conclusion The existence of echo chambers may explain why social-media campaigns that provide accurate information have limited reach and be effective only in sub-groups, even fomenting further opinion polarization. The introduction of dissenting information into a sub-group is disregarded and can produce a backfire effect, thus reinforcing the pre-existing opinions within the sub-group. Public health professionals should try to understand the contents of these echo chambers, for example by getting passively involved in such groups. Only then it will be possible to find effective ways of countering anti-vaccination thinking.

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  • Attitude-based homophily is particularly pronounced in segregated networks, such as scientific vs. conspiracy communities, and among groups divided by political affiliation, such as Democrats and Republicans.

    “This phenomenon is particularly pronounced in segregated networks, such as”

    From A systematic review of echo chamber research: comparative analysis of conceptualizations, operationalizations, and varying outcomes (2025) · cites this paper as [49]

    The Introduction (p. 2) describes users selecting belief-consistent information and forming polarized groups with opposing views that rarely interact. It does not establish that attitude-based homophily is particularly pronounced in such networks, or discuss scientific versus conspiracy communities or Democrats versus Republicans as the claimed examples. (LLM, conf=0.84)

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  • Previous work has shown that there is evidence of echo chambers on real social media platforms around information on vaccines in general.

    “Previous work has shown that there is evidence of echo chambers on real social media platforms around information on vaccines, in general 54,55 .”

    From Measuring the impact of COVID-19 vaccine misinformation on vaccination intent in the UK and USA (2021) · cites this paper as [54]

  • Most studies examined specific groups or communities on platforms, such as climate change deniers, vaccination opponents and advocates, and Trump supporters.

    “Most studies examined specific groups or communities on platforms, such as climate change deniers (e.g., [94]), vaccination opponents and advocates (e.g., [49]), and Trump supporters (e.g., [16]).”

    From A systematic review of echo chamber research: comparative analysis of conceptualizations, operationalizations, and varying outcomes (2025) · cites this paper as [49]

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Research works printed but not linked: 2

  1. [4][4] Zipprich, J., Winter, K., Hacker, J., Xia, D., Watt, J., Harriman, K., & Centers for Disease Control and Prevention (CDC). (2015). Measles outbreak-California, December 2014-February 2015. MMWR Morb Mortal Wkly Rep, 64(6), 153154. -
  2. [29][29] Pease, B. (2015). Fear vs. fact: The modern anti-vaccination movement. Harvard Science Review, March 2015. -

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Authors
Schmidt, A. L., Zollo, F., Scala, A., Betsch, C., & Quattrociocchi, W.
Affiliations
  • Ca' Foscari University of Venice (IT)
  • University of Erfurt (DE)
Corresponding author
Schmidt, Ana Lucía
ORCID
Venue
Vaccine
Publisher
Elsevier BV
Published
2018-06
Volume
36
Issue
25
Pages
3606-3612
ISSN
0264-410X (ISSN-L)
DOI
10.1016/j.vaccine.2018.05.040
OpenAlex
W2784018251
Cited by
403
References
25
Citations by year
2026: 16 · 2025: 54 · 2024: 41 · 2023: 54 · 2022: 77 · 2021: 69 · 2020: 64 · 2019: 23 · 2018: 5
FWCI
91.57
Type
journal article
Language
en
Open access
Licence
www.elsevier.com/tdm/userlicense/1.0/ (tdm)
Locations
  • Vaccine (publishedVersion)
  • PubMed (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • IRIS Research product catalog (Sapienza University of Rome) (submittedVersion)
  • ARCA (Università Ca' Foscari Venezia) (submittedVersion, other-oa)
  • arXiv (Cornell University)
Topics
  • Social Sciences › Sociology and Political Science › Misinformation and Its Impacts
  • Social Sciences › Health › Vaccine Coverage and Hesitancy
  • Social Sciences › Communication › Social Media and Politics
Keywords
vaccine hesitancy, anti-vaccination, opinion polarization, echo chambers, Facebook, social media, information segregation, community detection, backfire effect, public health communication
MeSH terms
Vaccination Refusal, Algorithms, Communication, Humans, Social Control Policies, Prejudice, Vaccination, Social Networking, Social Media

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