If new generations are not also given the vaccine, it will eventually return.
Probably the same with HIV, although I could see it being somewhat more difficult for that to make a resurgence. If we inoculated the entire human race against it, it could possibly eradicate HIV for several generations, if not permanently.
You mean the time the US admin was intentionally neglecting the epidemic because "it's a gay disease"? Why do you think Reagan would have done anything to ensure such a medication was easily available?