Vampires existed long before the church. They just have a brain disorder that gives them a seizure when they see straight right angles. Right angles don’t really exist in nature. Humans found out this and started making crosses. Humans created the church to maintain this knowledge during the vampires long hibernation periods of around 1000 years. (Credit to author Peter Watts “Blindside”)
I loved Blindsight (the name of the book is not Blindside) but that was one of the most ridiculous paragraphs I've ever read.
The natural world is filled with right angles. Many rocks erode into perfect right angles because of their cleave points. Saplings grow at right angles to the ground. Branches of older trees are sometimes at perfect right angles to the trunk.
Anyone who has gone on a hike sees right angles everywhere. Vampires couldn't walk a kilometer without a seizure from naturally occuring right angles.
Nah, vampires only hibernated a generation or two. Just long enough for prey populations to grow back to sustainable levels, and just long enough forget them and begin to scoff at grandma's crazy campfire tales.
Peter Watts - Blindsight
And yes, it's hard science fiction. With a vampire ship captain. Seriously.
Many versions free on the author's site. Give the prologue a spin.