A: That's a good question. I guess it depends on the android. Harkness probably wasn't in the situation to find out, so this is a nice open field.
B: I bet Harkness applied Stimpaks and it actually healed him. It's hard to believe he wouldn't have done that as Security Chief. Of course you can explain it away by relocating it to his programming that simply ignores such logical fallacies and convince Harkness that he is human. But I feel that defeats the point and stretches Fallout 3's lore too far.
So I'd say radiation and Stimpak healing could technically both affect an extremely advanced android (possibly more sophisticated than even A3-21).
However, we are not going to play an android.