This excellent piece by Michael Fitzpatrick in the Times of London shows what happens when enough people in a country with a lot of visitors stop vaccinating their toddlers against measles. You get a measles epidemic. Measles is a very serious disease that can kill.
A lot of the blame for this has to go to Andrew Wakefield and his bogus theory linking the MMR shot to autism. You can't fault the man for having a faulty hypothesis. But to continue profiting from it in the face of all scientific evidence is shameful, even more shameful to play the martyr when the scientific community refuses to jump in step with your foolishness.
Luckily, Americans are a bit more level-headed, or perhaps too busy watching YouTube to clue into the latest quack theories. The latest MMWR data show that vaccination rates are holding steady in the U.S., despite the scares that affect chunks of fearful parents in certain communities.