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Old June 7th, 2008, 11:53 PM
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Dr Lee Dr Lee is offline
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Lecture 2: Vaccine Associated Sarcoma - by Dr. Lee

VAS – Vaccine Associated Sarcoma.

Vaccine Tumors and Vaccine Recommendations for Cats
There is a lot of concern recently over cat vaccines and rightfully so. Unfortunately much of the reaction has lead to a lot of misinformation and questions leading to many pet owners either not hearing about it, having the information brushed over or avoiding vaccines which may be necessary for their pet. I hope this lecture will have the following effects: 1) hopefully convince people to never allow adjuvanted vaccines given to their cat, 2) provide understanding on vaccine related cancer and 3) provide links and information so cat owners can make a vaccine choice that is right for them.

Adjuvants. What are they?
An adjuvant is basically ‘something’ that makes vaccines work better. There have been two types of vaccines for a long time – live vaccines and killed vaccines. Live vaccines utilize the live virus which has been rendered ‘non virulent’ meaning that it does not create disease. A killed vaccine utilizes a virus which has been killed and ‘chopped up’. The advantage of a killed virus is that it is non possible for the virus to turn back into an active disease causing virus but the disadvantage is that they do not stimulate the immune system as well. Thus typically adjuvants are used to make killed vaccines work better.

How do adjuvants cause cancer?

First of all, while there is a lot of supporting evidence or adjuvants causing cancer along with an understanding of how they likely trigger cancer formation, an absolute link has not been established. With the presence of existing alternatives to adjuvanted vaccines, I do not see any reason at this time for any cat to receive an adjuvanted vaccine. So what is the theory behind the adjuvants? Well we know for a fact that adjuvants cause chronic injection site inflammation. It is this chronic inflammation which can act as a trigger for cancer growth. Some adjuvants contain aluminum which will persist at the administration site. One of the major concerns is also one of the reasons for some lack of ‘definitive evidence’. This concern is that the time frame from administration of an adjuvanted vaccine to cancer growth is 2 months to 10 years!

What type of cancer is it? How bad is it?
Well cancer is never good, but fibrosarcoma, the most common vaccine associated cancer, is particularly bad. If VAS is present then with a combination of surgery, radiation therapy and chemotherapy, the survival time is, on average 24-36 months. If only one of these options is utilized, the a general estimation on life expectance is 6-12 months post diagnosis. These figures are from Phil Bergman D.V.M., D.A.C.V.I.M. These are indeed scary figures for our pets. There are also other tumors that are thought to be associated, although less commonly than fibrosarcoma, with adjuvanted vaccines. They include: malignant fibrous histiocytoma, osteosarcoma (bone cancer), rhabdomyosarcoma (muscle tumor), liposarcoma (malignant fatty tumor), chondrosarcoma (cartilage tumor), and undifferentiated sarcoma. All of these are malignant and potentially fatal.

Should I still vaccinate my cat?
In a word, yes. Vaccines save lives every day. I do a lot of rescue work and cannot begin to adequately describe the suffering and death seen in both dogs and cats which could have been so easily avoided with vaccines. The good news is that with the recognition of this reaction, there are two forms of vaccines which are NOT associated with this cancer. The first is non adjuvanted modified live virus vaccines and the second is recombinant vaccines. For the combination vaccine which typically includes panleukopenia, rhinotracheitis and calici virus, both of these forms exist. For feline leukemia and feline rabies, only the recombinant vaccine exists. The non core vaccine FIV is only available as adjuvanted. I will go over each vaccine briefly.

This stands for Feline viral rhinotracheitis, calici and panleukopenia. It is also known as a ‘combo shot’ or 3 in 1 vaccine, etc.. This vaccine is available a modifiled live vaccine (MLV) non adjuvanted, killed adjuvanted and killed non-adjuvanted. There is also a MLV non adjuvanted intranasal form. The only form I recommend is a MLV non-adjuvanted. It can be obtained through several manufacturers including Pfizer and Merial. Both are fine however since the FeLV and Rabies which is non-adjuvanted is ONLY available through Merial. It is likely that the veterinary hospitals carrying three non-adjuvanted vaccines will likely be using the same company.

Recombinant Technology
The FeLV (feline leukemia virus) and rabies vaccines by Merial utilize recombinant technology. SO what is Recombinant technology? It takes the best of the killed virus vaccine and the live virus vaccine. Killed vaccines take just the ‘bits’ of the virus that the immune system would recognize and discard the rest of the virus. Recombinant vaccines take a live harmless canary virus and places the antigenically recognizable ‘bits’ of the virus insideit. Thus it is a live virus which cannot revert (unless you vaccinate a canary) and the selective properties of the killed virus. No adjuvants are necessary due to the live quality of the vaccine. Furthermore testing of the vaccines immunity have shown excellent immune response and protection against challenge. Bottom line – a technology breakthrough with the cats as the big winner!

This vaccine is often avoided and skipped by concerned cat parents. For those who should have this vaccine, please do NOT skip vaccination. The non-adjuvanted vaccine is very safe and highly affective. This vaccine has been known to cause more local inflammation than other vaccines so was for awhile thought to be the only vaccine causing VAS. We know now that this is not true. The nature of the vaccine does bring the concern of inflammation. When Merial developed the recombinant FeLV vaccine they found that the vaccine was still causing more than acceptable inflammation. This inflammation was found to be from the pooling of the vaccine under the skin. So Merial utilized a needless injector developed by the military. The Vet Jet sprays the vaccine by a puff of air under the skin which evenly distributes the vaccine. This eliminates any pooling of the vaccine. So if the FeLV vaccine is injected by a needle into your cat – it was NOT this vaccine. It can only be given with the device. Let’s get back to the cats though. Do all cats need FeLV vaccine? Yes and no. When they are a kitten, all cats should get this vaccine. After the initial set, then there are options. I personally like a booster at a year of age. Some practictioners do not. After a year of age, the FeLV can be given either yearly or every three years for cats that are AT RISK. It is important to know that all cats, even those never vaccinated, naturally develop immunity against FeLV after a year of age. So cats under a year of age, need protection. FeLV is a terrible and inevitably fatal viral disease. We need to protect our kittens from it. Cats over a year of age, should be vaccinated based upon owner comfort and patient risk. I will have some more concrete recommendations at the bottom.

Not all states require rabies vaccination in cats. My state does not. I still recommend this vaccine for most cats though. Rabies virus infections do still happen here in the US and worldwide. If infected in a human, it will, if not aggressively treated early, kill you. Since a recombinant form of the vaccine is available for cats, then the benefit versus risk is clearer. Whether you vaccinate your cat for rabies or not though however is an individual choice. Some cats are very sensitive to vaccines and live a pampered indoor low risk life style and some cats spend some time outside in a high risk environment.

Feline Immunodeficiency Virus (FIV) is analogous to HIV in humans. It is another infectious virus with fatal implications. It is typically transmitted by a bite wound. The vaccine – sounds great to have a protection against AIDS right? Well not exactly. First of all it only comes adjuvanted. That is problem one. There are more problems however. There are five clades (basically strains) of FIV. The vaccine was only designed to protect against clades A and D. When it was tested it only was tested against clade A. For those in Canada, the FIV strain typical to your area is clade C – which the virus was neither designed for nor tested for. While the efficacy for clade A was not bad (82%), there are four strains that we don’t know if the vaccine work at all for. Not enough problems? How about this? Once vaccinated the cat will test positive, sometimes forever and it is not possible on blood work to adequately differentiate between vaccine induced positive and a true positive. When I talked to the Forte Dodge representative in April 2007, their data revealed that at one year post vaccination 30% of cats will test negative again but still be protected against challenge. No other data existed at that time according to them. So what about the other 70%? How long does it take for them to test negative? No way to know according to the vaccine representative. This makes up for a lot of concern about this vaccine. For this reason, many veterinarians do not use this vaccine.

The other vaccines.
Yes, there are more… but this lecture is on adjuvants. The links I provide at the bottom will go over those other vaccines.

Vaccine recommendations.
Dr Alice Wolf is a veterinary specialist who I have great respect for. She currently is a consultant on our veterinary information network (VIN) and a champion of non-adjuvant vaccine promotion. Here is her response on vaccine protocols for cats:
MODIFIED LIVE FVRCP starting at 6-8 weeks of age, give every 3-4 weeks out to 16 weeks.
Merial PureVax RV at 12 or 16 weeks (whatever is required for age in your area)
Merial PureVax FeLV at 8 and 12 weeks for ALL kittens
Year One: MLV FVRCP, PureVax RV, PureVax FeLV IF the cat is still at risk.
After that: MLV FVRCP every 3 years, PureVax RV yearly (until 3 year approval is completed), then q3years, PureVax FeLV yearly if cat is still at risk.
I give NO:
Virulent Calici

-Alice M. Wolf, DVM, DACVIM, DABVP
Discussion date January 6, 2008.

What if my vet recommends something else?
That is okay, as long as the vaccines are not adjuvanted. What if I want to do a different plan? That is okay too. First each patient has a different life style and demographic. Secondly the protocols are ever changing .

Why don’t all veterinarians carry only non-adjuvanted cat vaccines?
I don’t really know. One answer is price, they are more expensive. The other is familiarity. Neither really makes sense. The price, while many times that of cheaper options, is still only going to lead to a few dollar increase in the owner’s cost. Also does price matter when we compare the potentially cancer causing vaccine and the non cancer causing vaccine??!

What if my vet does not carry this vaccine option?
Well, for the vaccines at least, go somewhere else or try to convince that vet to carry them, if she or he has that decision making ability.

Some additional resources:
AAFP Vaccination Guidelines

AAFP home

AAFP Vaccine guidelines (condensed version – easier to read!)

Merial Recombinant Vaccine Information

Fact Sheet on VAS written by Dr. Wendy Brooks

Vaccine Associated Feline Sarcoma Task Force

There is still much information that is needed and this topic is ever changing. For the time being, it is important that as we protect our cats from infectious disease we do this as safely as possible. I hope this lecture provides the information in a straight forward and useful format. Again, if there are other topics that would be of interest or if there are suggestions, please let me know.
Christopher A. Lee, DVM, MPH, Diplomate ACVPM
Preventive Medicine Specialist With a Focus on Immunology and Infectious Disease
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