Despite the efforts of anti-vax people, progress towards a solution does continue.

When parents are desperate to understand the reason THEIR child is disabled, they'll believe anything that SOUNDS half way plausible. Once they've decided to believe in it, they feel closure and their emotions become invested in that belief. In this case, that includes anger at the "evil", "greedy" vaccine manufacturers.

Once strong emotions are tied up in a belief, it's awfully hard to shake that belief, even when facts prove the belief wrong.