WaPo:

Facebook is conducting a vast behind-the-scenes study of doubts expressed by U.S. users about vaccines, a major project that attempts to probe and teach software to identify the medical attitudes of millions of Americans, according to documents obtained by The Washington Post.

The research is a large-scale attempt to understand the spread of ideas that contribute to vaccine hesitancy, or the act of delaying or refusing a vaccination despite its availability, on social media — a primary source of health information for millions of people. It shows how the company is probing ever more nuanced realms of speech, and illustrates how weighing free speech vs. potential for harm is more tenuous than ever for technology companies during a public health crisis….

Some of the early findings are notable: Just 10 out of the 638 population segments contained 50 percent of all vaccine hesitancy content on the platform. And in the population segment with the most vaccine hesitancy, just 111 users contributed half of all vaccine hesitant content….

The research effort also discovered early evidence of significant overlap between communities that are skeptical of vaccines and those affiliated with QAnon, a sprawling set of baseless claims that has radicalized its followers and been associated with violent crimes, according to the documents.