I hate to say this, but I feel cheated - not because there's no sex, but because the story seemed rushed.
I thought you had a wonderful idea. The concept of muggle-borns being the true centers of power and that being a reason for the pureblood hatred of them is somewhat rare. And I was intrigued by the idea of Hermione's blood being the element Severus needed to cure himself.
In all honesty, though I was intrigued by the idea, it seems as though you attempted to force the story in a direction it was not quite ready to go. Severus and Hermione do not yet know each other well enough to connect emotionally on the level you seem to want them to.
You've set a wonderful stage with chapters one and two. But in chapter three, after the antidote is consumed, the reactions seem forced and somewhat trite.
It would be interesting to see the relationship that you want to develop between Severus and Hermione. The romance between them is appreciated. The characters of your story, though, do not yet seem to be ready for that interaction.