I have just posted something regarding the vaccination and I am personally not in favour after what happened to my pony. It is looking as though the vaccination could be the problem. Two other people have also replied to my thread, I would have a read if I were you.
My vet won't give it as he says it isn't very effective and often makes horses ill. He also says that if a yard has a case it is generally better to keep a very close eye on all the other horses as quick diagnosis can make the difference. I personally wouldn't have it done.