When you bring your cat to the veterinarian for her rabies and leukemia vaccines, do you ask what vaccine your vet is using?
If not, you should.
Rabies and leukemia vaccines on the market for cats have been known to cause tumors at the site of injection. These are called vaccine-induced sarcomas. There are now much safer vaccines available that do not cause these devastating tumors.
In my opinion, your veterinarian should be vaccinating your cat with the safer vaccines. (Vaccine-induced tumors have been reported in the dog and the ferret, but they are extremely rare.)
Why Is the Newer Vaccine Safer Than the Older One?
The older vaccines have something in them to boost their effectiveness. This is called an adjuvant. The inflammation caused by the adjuvant is what is thought to cause the tumors. The newer vaccines do not have adjuvants in them, but they have been proven to work just as well.
Bottom line: The newer rabies and feline leukemia vaccines are effective, and they are not causing tumors.
So Why Isn’t Everybody Using Them?
You tell me. The new rabies vaccine’s biggest drawback, in my opinion, is that it is labeled only for one year rather than three years. This is not because it is less effective. It is probably effective for many years, certainly more than one year.
Unfortunately, during the testing of the vaccine to get USDA approval, the study fell short of getting the three-year label. So your cat needs to be given the vaccine annually. More on this later…
Is the Tumor a Big Deal?
Yes, it’s a BIG DEAL. It can be fatal.
These sarcomas that arise at the injection site are very aggressive tumors. Studies (none are conclusive) say these tumors occur in anywhere from 1 in 1,000 cats to 1 in 5,000. We do not have enough information to give an exact number. Geography (where the cat lives) and genetics may also be risk factors for tumors development.
The tumor that arises at the injection site can take a few weeks to many years after a vaccination is given. If a lump is present for more than a few weeks after a vaccination, the standard of care is to biopsy the lump. If it is a vaccine-induced sarcoma, a radical surgery to remove it is performed, with very wide surgical margins. This may mean an amputation. Radiation may be needed after the surgery.
Despite all this, too large of a percentage of these tumors return. The cat may end up being euthanized.
Okay, So Why Is Dr. Deb So Up in Arms?
I’m probably on such a soapbox about this topic because I have seen more than my share of these tumors, and I don’t want to see any more. If we have a way to prevent these now, I want everyone to know about it.
Here’s how we got into this mess in the first place:
- The rabies vaccine was changed in the late 1980s by the USDA from a modified live rabies vaccine to a killed virus vaccine. Why the change? Some kittens vaccinated in California in the 1970s with the modified live vaccine actually developed rabies. By changing the vaccine to the killed, adjuvanted form, the USDA was unaware that tumors were a potential side effect.
- Rabies vaccination in cats became mandatory, depending on which state you lived in, beginning in the late 1980s.
When I began practicing in 1988, you might say it was a perfect storm: The only rabies vaccine approved was the vaccine with the potential for tumor formation (unbeknownst to everyone); the rabies epidemic was in full swing in Pennsylvania, with cat owners panicking; and the government passed mandatory rabies vaccination for all cats.
It took a number of years to prove that the vaccines were, indeed, causing the tumors, and additional years to come up with a safe vaccine. Veterinarians and educated owners have been putting pressure on the pharmaceutical companies to make a safer vaccine. And now they’ve done it! So… why isn’t everybody using it?
- Expense? The safer vaccines are a bit more expensive — but not by much. I keep the price as affordable as possible. In the grand scale of what veterinary bills can be, this is an absolute pittance to pay for better safety.
- Inconvenience? The one-year label for the rabies vaccines is a mild pain in the neck, but look at the alternative. Just come in every year for your rabies vaccine, particularly if your cat goes outdoors. Simple. A quick annual visit versus the possibility of a tumor eating away the leg of your cat? I don’t think there’s much of a decision there.
- Method of Injection? The new leukemia vaccine had to be given with a special device that was not terribly cat- or user-friendly. That’s fixed now. It’s a regular, simple vaccine. End of story.
Why Do You Have to Get It Every Year?
In the future, the rabies vaccine should be approved for three years.
Why does it not have that three-year label currently? When the company was doing the testing for the new vaccine, not enough cats in the non-vaccinated group died of rabies. You heard me! In order to get a new vaccine approved, a pharmaceutical company has to challenge a vaccinated group of cats with the actual disease (rabies), and also challenge a non-vaccinated group with the disease.
The rabies virus used for the challenge is supplied by the USDA. Because the tests did not result in the USDA-required number of fatalities among the non-vaccinated group, the vaccine did not get approved for the three-year duration.
These studies are very expensive, very lengthy and, obviously, horrible to conduct. I’m happy to live with the one-year licensing right now rather than have more cats killed in the line of research.
These safer vaccines have been around for about 10 years now, and we are not seeing tumors associated with them.
I urge you to follow your state’s guidelines regarding rabies, particularly if your cat goes outside. But make sure you are giving your cat the non-adjuvanted rabies vaccine.
The leukemia vaccine, in my opinion, should be given to young cats and kittens, as well as older cats who are at risk. “Risk” means a cat who roams outdoors and has the potential to be exposed to leukemia-positive cats. Young cats are most at risk, so I think it is a good idea to vaccinate them with the non-adjuvanted vaccine. If they have no exposure later in life, you don’t have to continue to vaccinate them.
As part of the Veterinarian’s Oath, we vets promise to dedicate ourselves to “the prevention and relief of animal suffering.” If I can protect my patients from disease, and also cause them no harm, that’s what I’m going to do!
That’s what we all should be doing.
Photos (from top to bottom): ManhattanCatSpecialists/Flickr, istockphoto, lastquest/Flickr
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