It seems like a lot of dogs can handle the shot with no problems.....but there's those perfectly healthy dogs that have reacted badly or even died from it. It seems to me (from what I read, I don't know for sure) that if your dog has already had the injection with no problems, there probably won't be any problems. But I've never tried it before, and the chance of a bad reaction to it is just too big of a risk for me to take.