Yeah, that's why the usual solution is to cobble together a bunch of different 90% solutions until you have something pretty close to a 100% solution. Scientists are going through something similar with fighting wheat rust (which you've probably never heard of, but it'll be an important problem if it gets out of control).
The problem with HIV is that every obvious way of attacking it seems to have some kind of drawback that's less than obvious. You can sit around and think up all kinds of hypothetical scenarios for attacking it and find that people have already tried that. And failed.
I guess should have known that the people around here would know what wheat rust is. But yeah, that stuff is pretty nasty, as far as its ability to kill wheat goes.
The problem with HIV is that every obvious way of attacking it seems to have some kind of drawback that's less than obvious. You can sit around and think up all kinds of hypothetical scenarios for attacking it and find that people have already tried that. And failed.