They don't - but there's a difference between faith and blind faith, and the latter is what is all too often followed in making medical decisions (for ourselves and for our pets). Again, there is no medical/scientific reason to vaccinate our pets annually - and there never has been. There is now scientific proof that immunity from vaccines lasts at least seven years, and probably the life of the dog. (In other words, it wasn't that after seven years the immunity was gone - it was that after seven years, the study ended.) Yet some people - even some vets, who you would think would have quite a lot of faith in medicine/science - refuse to acknowledge these medical/scientific facts, and continue to vaccinate every dog, for every thing, every year.I just don't see why living healthily and having faith in medicine/science have to be mutually exclusive.