My horse got an abscess from the needle, they called it a sterile needle abscess. Was really bad, when it finally came out through his neck. He was on 2 ABX, colic and had a running fever for days..Very scary.
My horse has had severe reactions to vaccines. The first time she reacted, the first symptom that we noticed was muscle twitching over most ofthe trunk of her body. Within a short time, she was displaying symptoms of anaphylactic shock. Since she had never reacted previously, and had been given all of her vaccines at once, we had no idea to which one she reacted. There was no localized swelling or stiffness. At subsequent vaccinations times, we gave her banamine and one shot at a time. Her allergic reactions often did not display themselves until several hours later ( once over 24 hours later as laminitis). We were finally able to determine that not only was she reacting to a particular brand of vaccine but also to any brand of the rhino vaccine. We also realized that each reaction was more severe than previous ones so I would caution you to watch very carefully any horse who displays muscle twitching after a vaccination.