The Walking Dead 4.10 "Inmates" (spoiler alert!)

[Umbran]

...and prevents them from rising up to snack on you.

Not very well. We've seen burned walkers move. It takes a hit to the brain to really stop 'em.

I'm guessing that after killing them, Lizzie *dissected* them. I imagine Carol might try to cover that until she could try to correct Lizzie...