Seth Mnookin is the author of the just-released The Panic Virus (Simon & Schuster), from which this essay is adapted. Blog posts and other updates can be found at http://thepanicvirus.com and you can follow him on Twitter at @sethmnookin.

Recent reports have demonstrated that Andrew Wakefield’s study linking the MMR vaccine to autism was fraudulent, but Seth Mnookin says we’ve known this for years—and yet people still believe in the link.