When I asked why there is no human equivalent of flea/tick drops my vet said it was because "when you only live to be 20, you don't worry about smoking when you are 10."

I think the original, mouse brain derived Japanese Enephilitis vaccine, now discontinued, caused symptoms years later.

But prions were the cause, and those are slow acting.

The new, safer vaccine is only recommended if you're going to Japan or surrounding areas, and planning to going outside the city.