Unholy Embrace a vampire novel - vampires and the development of blood banks.

“During the latter part of the middle Ages, mortals became more sophisticated in their ability to hunt down and kill vampires. Vampires needed to kill deer and even cattle to supplement their diets.”
In The Vampires among Us by Thaddeus Romans

Vampires can survive by taking blood from cattle and other animals. However, these are poor substitutes for human blood, and vampires are not at their full strength when surviving only on animal blood. The development of blood transfusion technology meant the vampire no longer had to kill to obtain blood. In 1818, Dr. James Blundell a British obstetrician performed the first successful blood transfusion of human blood, for the treatment of postpartum hemorrhage. In the 1910s, it was discovered that by adding anticoagulant and refrigerating the blood it was possible to store it for some days, thus opening the way for blood banks. Naturally, vampires were very interested in obtaining access to blood banks. Groups of them use the money they had accumulated over the centuries and created their own blood banks. Most of the blood from such banks was utilized by mortals, but the vampires made sure their own needs were met first. In Unholy Embrace, Nessa, the female vampire, becomes a partner in an early, experimental blood bank.

 http://www.writing.com/main/view_item/item_id/1639917-Unholy-Embrace----First-Three-Chapters