Surprizing Answers to 2 Important Vaccine Questions

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  1. Isn’t there a special rabies vaccine for cats that does not cause vaccine sarcoma cancer?

Yes, and no.

There is a line of vaccines (Purevax from Merial) that was developed with vaccine sarcoma cancer in mind. When vaccine sarcoma cancer was first recognized in the 1980s, it was thought that the adjuvants in the vaccine were responsible for inciting the cancer. (Adjuvants are chemicals that increase the immune response to the antigens in the vaccines) Purevax vaccines are made without adjuvants.

Unfortunately, two more recent studies (here and here) show that the non-adjuvanted vaccines are just as likely to cause cancer as other vaccines. In fact, it is now clear that it is not just vaccines that can cause these cancers. ANY INJECTION can cause a tumor if given to a cat that is genetically predisposed. Now, the term “vaccine sarcoma” has been replaced by “injection site sarcoma.”

  1. Is there a difference between the 1-year and 3-year Rabies vaccines?

Maybe, maybe not.

There are some rabies vaccines that are labeled to give 1 year of protection and others that are labeled to give 3 years of protection. However, the first time a rabies vaccine is given to a pet, by law, it is only good for 1 year even if a 3-year rabies vaccine is used.

Here’s an interesting case in point. The Purevax rabies vaccine was tested at one year after vaccination. (Testing involves exposing vaccinated cats and an unvaccinated control group to the rabies virus) It passed the test so was issued the 1-year label. This is why many veterinarians are vaccinating cats yearly for rabies.

Now, the vaccine was also tested at 3 years post-vaccination. Although the vaccinated cats did not die when exposed to rabies, the 3-year vaccine FAILED the test. The problem was that the unvaccinated cats did not get ill either. It turns out that the challenge was not effective and Merial had to start over.

So, Merial threw in some extra antigen (nobody knows how much more) and started the process again. Three years later the challenge study was a success and Merial recently came out with a Purevax 3-year rabies vaccine. Unfortunately, they charge 3 times more for it, making the vaccine prohibitively expensive.

Besides, as the studies mentioned above prove, the Purevax vaccines are no more effective at preventing injection site sarcomas than any other vaccine. The bottom line is that you should get your cat the 3-year rabies vaccine to cut the number of vaccines he gets.

6 replies
  1. Rachel
    Rachel says:

    Hello Dr. Doug,

    I know that they now have the Purevax 3 year rabies, yet finding a vet that not still only using the 1 year Purevax is virtually impossible. What gives?

    • Dr. Doug
      Dr. Doug says:

      Purevax 3-year is 3X more expensive than the 1-year. Since Purvax came out there has been no decrease in sarcomas which seems to indicate that it does nothing to reduce the chances of the cat getting cancer.

  2. Linda
    Linda says:

    My cat died 3/2015 from an injection-associated sarcoma at 10 years of age. The tumor was right at the site where he got injections, on the scruff of his neck, and it metastasized into his brain stem. One day he got really lethargic and the vet wasn’t sure what it was, she put him on an oral antibiotic and pain medication and did blood tests. A week later he couldn’t walk. They did x-rays and found the sarcoma. I had to have him euthanized. It was injection induced. I wasn’t aware cats were being over-vaccinated until too late. I have anxiety about vaccinating my other cat now, she’s 12. I’m having trouble finding a vet who uses the 3 year Purevax. I would like her to get that one so she doesn’t have to get injections so often. I don’t care about the cost. I care about protecting my pet. I suspect it’s the vets who don’t want to do the 3 year vaccines. If your cat has the 1 year rabies injection 3 years in a row, that’s still 3x the cost. What is the difference?; probably something to do with money, no doubt. I think pet owners need to be educated about the issues with over vaccinating/injecting pets and most vets aren’t doing that.

    • Christine
      Christine says:

      I am very sorry about your loss of your cat. Please see my reply to Elizabeth below about difficulty finding 3yr Rabies Purevax. You might even contact Merial who may have info on who may have it near you.

  3. Elizabeth
    Elizabeth says:

    This article must be old as a low cost spay/neuter offers the 1 yr rabies OR the 3 year rabies and there’s not much at all difference price wise. You have to consider each time you get the 1 yr you have to add the office visit price, that then makes them just as much or more than the 3 yr.

    • Christine
      Christine says:

      They are talking about Merial Purevax non adjuvanted vaccines which cost more and the ones labelled for 3 year cost even more. A veterinarian cannot purchase these individually but rather a tray of 25 – they cost around 35 dollars a vaccine. Most clients because of the charge difference choose to do a 1 year Purevax, so if the others were ordered most of the remaining would expire before use and be tossed at a cost loss of probably 500 plus dollars or more. That is probably why it is difficult to find them available.


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