A small percentage of the world's teenagers are changed into vampires when adolescent hormones trigger a strand of what is otherwise known as junk DNA.

 The change from human to vampire takes four years, during which time the adolescents known as "Fledglings" must attend one of the "House Of Night" boarding schools. 

While there, they are required to take the vampire sociology 101 course to learn the dangers they face. 

If a fledgling is not in constant proximity to adult vampires they will die; so they rarely leave the school. About one in ten fledglings die anyway, since their bodies cannot tolerate the change. 

For those who survive there's a big reward: Vampires are physically stronger, with accelerated reflexes, enhanced dexterity, life of more than five centuries, as well as heightened senses such as night vision.