Why do they hold a West Nile vaccine for horses but not for humans?
Answer:
Perhaps the equine vaccine was originally designed for human use but cause too many bad effects in humans and be relegated to animal use.
But there is a WNV vaccine surrounded by the works for humans. It is unknown when, if ever this will hit the market.
A horse's natural life is worth more than a man's.
The testing and approval process is more stringent and time consuming for human medication and vaccines than it is for animals.