title: Greater freedom of speech on Web 2.0 correlates with dominance of views linking vaccines to autism.
abstract: BACKGROUND
  It is suspected that Web 2.0 web sites, with a lot of user-generated content, often support viewpoints that link autism to vaccines.
  
  
  METHODS
  We assessed the prevalence of the views supporting a link between vaccines and autism online by comparing YouTube, Google and Wikipedia with PubMed. Freedom of speech is highest on YouTube and progressively decreases for the others.
  
  
  RESULTS
  Support for a link between vaccines and autism is most prominent on YouTube, followed by Google search results. It is far lower on Wikipedia and PubMed. Anti-vaccine activists use scientific arguments, certified physicians and official-sounding titles to gain credibility, while also leaning on celebrity endorsement and personalized stories.
  
  
  CONCLUSIONS
  Online communities with greater freedom of speech lead to a dominance of anti-vaccine voices. Moderation of content by editors can offer balance between free expression and factual accuracy. Health communicators and medical institutions need to step up their activity on the Internet.
authors: Department of Neurology, University of Alabama Birmingham, Sparks Center Suite 350, 1720 2nd Avenue South, Birmingham, AL, USA. Electronic address: anandv123@gmail.com.
authors: Anand
authors: A
authors: Venkatraman
authors: Department of Medicine, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, USA.
authors: Neetika
authors: N
authors: Garg
authors: Department of Medicine, Cambridge Health Alliance/Harvard Medical School, Cambridge, MA, USA.
authors: Nilay
authors: N
authors: Kumar
mesh_terms: D001321:Autistic Disorder / Q000209:etiology*; D005610:Freedom; D006801:Humans; D020407:Internet; D039781:PubMed; D061108:Social Media; D013060:Speech; D014612:Vaccines / Q000009:adverse effects*
chemical_list: D014612:Vaccines
keywords: Autism; Free speech; Internet; Vaccines; Web 2.0