President Donald Trump\u00a0and his head of Medicare and Medicaid Services Dr. Mehmet Oz are at odds over the MMR vaccine. Here's what to know.

A doctor fact checks Dr. Oz and Rep. Byron Donalds claims on vaccines and measles during their recent CBS appearances on "Face The Nation"

A doctor fact checks Dr. Oz and Rep. Byron Donalds claims on vaccines and measles during their recent CBS appearances on "Face The Nation"