Good question - and I can tell you a bit of my experiences with this issue. My 6 yr old cat Daisy passed away due to "vaccine- induced sarcoma" which is a cancerous tumor caused by one or more of the annual shots.

My understanding is that cats in general have a fairly unusual immune system (compared to other mammals like dogs and humans). The problem seems to come when injections are given all in one place (for instance, the back of the neck at the shoulder blades).

Current wisdom in the veterinary world is to give the yearly shots in various places instead of one place. For instance, one shot in the front leg, one in the back leg, etc. This prevents the concentration of the vaccines from working together against your cat's immune system. To be brutally honest about this procedure - if a cat gets a tumor from one particular vaccine, the leg is a much easier area to remove than a tumor near the spine. This sounds very scary, but in fact not that many cats get this life-threatening reaction.

There is also some question about just which one of the vaccines causes this reaction - or is it a combination of them ??? So, your concern about giving "indoor only" cats too many shots is a good one. My vet has recommended for my indoor cat that he only receive a minimum of vaccines. But, if he goes outdoors, or I bring in another cat that goes outdoors, he will need to get more shots just in case.

It is very sad to know that the shots which were meant to help your pet has actually hurt them. But, I still believe that vaccines are important and helpful as long as you are educated about the pros and cons.

Best wishes to your furry family -