Herpes vaccine is useful if you have cause to consider that she might be carrying the herpes virus. Herpes virus causes small litter sizes, fading puppy syndrome and early feotal loss. If you are not seeing these sypmtoms with your other bitches, then you probably don't have the virus in your household at this time. I tend to only use the vaccine in animals that are either coming from an envoronment where we know this can be an ossue, or if there have been these issues in prevous litters.
When I do use the vaccine we usually see bigger litter sizes and stronger puppies. I have not see any ill effects from the vaccine in the animals I have treated.
The vaccination protocol is to give 1 dose of the vaccine 1 week after mating and one dose 1 week before whelping. We do this in every pregnancy as there doesn't seem to be much longevity to the vaccine.
I hope this answers your questions but if you want any more information please don't hesitate to ask me.