I struggled with this recently when my dog Barney threw a positive on a leptospirosis
http://www.yorkietalk.com/forums/sic...ospirosis.html
After all was said and done, I was advised to give the vaccine and then I was advised not too - my vets could not agree. Over the years, I've had more vets tell me to give the vaccine than not, but I have decided against it. The older ones have had it in the past but my youngest dog has not.
This is a tough one. Leptospirosis is a horrible disease. The dog is usually very sick when the vets diagnose it. I still am not giving the vaccine at this point and I really hope I don't come to regret it.
Good luck with your decision!