One of the side effects of the shingles vaccine is "shingles-like symptoms." So if you take the shingles vaccine and get shingles, doctors assume that it *can't* be shingles, so they call it a shingles-like rash.

I think other vaccines have similar notes in their side effect list ("measles-like symptoms" and so on).

It's so absurd it's hard to even explain to people.