cyst on my cat

Question
QUESTION: My cat recently got a one year rabie shot and he now has a rather large cyst in the same area. Is there any connection?

ANSWER: Depending on how recently the vaccine was given it could be one of a couple things.  If just in the last day or two it could be an inflammatory reaction to the vaccine that should subside.  

If it has been longer there is the possibility of an abscess or a rare injection site tumor called a fibrosarcoma.  In this case, or it existing longer than briefly after the vaccine I would recommend having him examined by your veterinarian to check the nature of the problem.

Best of luck to you and your feline friend.


---------- FOLLOW-UP ----------

QUESTION: My vet insists that i get the cat in tomorrow. The cyst was not there until after the shot so, whose at fault? the cat has had several rabies shots without a reaction so I tend to think it was the administration of the shot that caused this. Your thoughts? thank you.

Answer
Immune reactions to vaccines can occur even after an animal has received the vaccine previously without a reaction.  In fact this is very likely with many allergic type reactions.  The individual is presented a substance whether it be something in a vaccine or medicine or something in a type of food.  The body then in response to this substance (referred to as the allergen) creates antibodies that react when the same substance in presented at a later date.

Since this "cyst" has stayed around for more than just a day or two it is possible that there could be an abscess at the injection site.  This would be very rare but is theoretically possible.  When vaccines are administered the needle must push through the layer of skin, which like all skin has bacteria at it's surface.  Bacteria travelling along with the needle could possibly cause an infection.

Vaccination problems and reactions tend to be rare but can happen.  Like many things it is a matter of risk vs benefit, where the chance of a rarer and treatable problem is preferred to a deadly illness that also threatens human life.  It is unfortunate when problems arise however and I hope that your cat will be healthy again soon.  Best of luck.