Ah, I see. That makes sense now; your previous example had led me to believe that the difference was much greater than it is. I had been using "vague" to mean that it didn't sharply limit the number of anticipated experiences; there are lots of things that are harmful that cover a range of experiences, and so saying that something will "cause harm" is vague. For the disease question, "vague" would be saying "he has a virus"; while that term is very clearly defined, it doesn't tell you if the person has a month to live or just has this year's flu, so the worlds in which the statement is true can vary greatly and you can't plan a whole lot based on it. Ironically, my definition seems a lot vaguer than yours now that they've both been defined.

And now I can happily say the matter's resolved.