One of mine had a reaction once- but not a bad one like your experience.
He developed a large, hard lump where he received the shot. It didn't hurt or appear to bother him in anyway. It was kind of like scare tissue, I guess. Over time (months) it went away. My vet checked it several times and said as long as it wasn't bothering him and continued to shrink to leave it alone.
The next time he got his shot he didn't develop any lump at all. |