If you decide to wade into this one at the dinner table, we'd recommend calmly explaining that this idea started with a now thoroughly-debunked — and retracted — study of only 12 children that appeared in 1998 in The Lancet, which claimed there was a link between the MMR vaccine and autism.

That study was not only flawed, but it also sneaked in false information to try and make its point.

Since then, numerous studies that have analyzed data from more than a million children have shown that there's no connection between vaccines and autism.

Fears about that connection persist because of public figures making (unknowingly or otherwise) false claims about vaccines. This has led to scary diseases like measles coming back and to vaccination rates in some wealthy Los Angeles neighborhoods that are similar to those in Chad or the South Sudan.