Are all feline vaccines created equally?
Years ago, veterinarians started to see, infrequently but consistently, cats with cancerous tumors in the area that vaccinations were being administered. These tumors, called fibrosarcomas, are very invasive tumors that are nearly impossible to completely remove surgically.
Many studies have been done over the past 25 years on this phenomenon. Incidence rates were gathered and they were low. Generally 1 out of every 5,000 cats is affected. Studies showed that the cats that develop these tumors have some sort of genetic variation for this to occur. So, these tumors are certainly not strictly related to vaccinations. So, why then, did the location generally seem to correlate to vaccine sites?
Prior to seeing the formation of these types of tumors, the majority of feline vaccines were killed virus vaccines. What this means is that the virus in the vaccine (namely Rabies and Feline Leukemia) has been killed so it can’t be infective to the cat. However, the immune system does not mount much response to a killed virus, making many of these vaccines less effective. Thus, an adjuvant substance is added to the vaccine to stimulate an inflammatory response.
When pathologists started examining these tumors following surgical removal, it was noted that there were particles of this additive within the tumor cells. An aluminum based adjuvant is the most commonly used. The initial suspicion was that the adjuvant was causing these tumors to form; but then, tumors starting showing up following other injections such as long acting steroids, flea prevention and microchips. This is when it was realized that there had to be other factors involved.
However, it was still quite concerning that the aluminum additive was noted within the tumors. It became apparent that a non-adjuvanted form of vaccine was needed to improve the safety and overall health of our cats.
We are fortunate that in the past 15 years, studies have led to formulation of non-adjuvanted, very effective vaccines for Feline Leukemia and Rabies. There has been a drop in frequency of the tumors since many veterinarians have started using these vaccines. There are still cats who are going to develop these tumors but the risk has certainly been reduced with the newer vaccines.
This is why, the veterinarians of CHFA and BVAC, decided many years ago to recommend only this type of vaccination for your cat. This vaccine is a bit more expensive but knowing what we know about this condition, the reduced tumor risk associated with these vaccines is worth it.
You may also have noticed that we give the vaccinations down in the limbs instead of at the shoulder blades. The reasoning for this is two-fold: 1) it gives us a better chance of being able to fully remove the tumor by amputating the limb and 2) each vaccination is given in the same location on all cats thus making it easier to notice any trends associated with a particular vaccine.
We are committed to providing the best care to your cat and we want you to understand the reasons behind the recommendations we make.