The Passage trilogy readalong discussion

Just wondering whether you agree with Justin Cronin / the Publisher's choice to call the book 'The Passage'. Can you see why the book was called this? Would you have chosen something different?

Spoiler - for anyone not done with The Passage yet.

Towards the end of The Passage there's a whole bit about the various characters entering and trans versing a passage and I thought that the title finally made sense. However when Amy destroyed the serum, I though that action also sort of derailed the title of the novel as well.