David Gorski gives the anti-vaccine airheads the Dickens.
Basically, the design of the Hornig study study was pretty simple, and, better yet, it was an intentional attempt to replicate the research of Andrew Wakefield using rigorous methodology. The design was a case control study in which children with autism and GI problems were compared to children with GI problems and no autism for a number of parameters, including MMR vaccination and the presence of measles virus RNA in the gut of children who underwent endoscopy. The overall approach was to determine whether children with autism and GI symptoms were more likely to have detectable measles virus RNA in the gut. The result?
Zero correlation. Nada. Zip.
Vaccinate your kids.