Passage Trilogy Series by Justin Cronin

The Passage Trilogy by Justin Cronin is a post-apocalyptic saga where a government experiment unleashes a deadly virus, creating vampire-like creatures called "virals." Humanity's survival hinges on Amy Harper Bellafonte, a mysterious girl who holds the key to stopping the plague.

• The Passage
  A government experiment goes wrong, unleashing a viral apocalypse, while Amy, an immune girl, may be humanity’s last hope.
• The Twelve
  Survivors uncover the origins of the virus and the truth about the powerful Twelve, leaders of the virals.
• The City of Mirrors
  The final battle between humanity and the virals decides the fate of the world as Amy faces her ultimate destiny.