Much of the concern surrounding annual pet vaccinations stems from the belief that vaccines may play a significant role in the formation of tumors in cats. In a newly published study involving 662 cats with sarcomas, Dr. Philip H. Kass of the University of California – Davis concluded that vaccines alone were not the sole cause for the tumors. Rather, Dr. Kass suggested that the role of genetic disposition likely represents “”an additional and important component cause,”” given the small fraction of vaccinated cats that actually develop sarcomas. Dr. Kass recently talked about his findings.
Note: Dr. Philip Kass was not paid for his interview with Goodnewsforpets.com and Dr. Kass has not received either personal or research funding by any of the Goodnewsforpets.com website sponsors.
Were you at all surprised with the results of your feline sarcoma study?
I guess I was neither surprised nor unsurprised. I went into this study totally open-minded about what we might find. I didn’t go into it with any pre-existing ideas.
What was most intriguing about your findings?
One of the most interesting findings was simply that we couldn’t discern any differences in the potential for different brands of vaccines to be causing sarcomas. We couldn’t show that one brand was any more or less likely than another to cause sarcomas.
Has the Vaccine-Associated Feline Sarcoma Task Force commented on your results?
I haven’t heard from them directly on it, but one of their members asked me if I would participate with some other people in a roundtable discussion on this or if I could present it in a way that is more accessible than a scientific paper. So that’s something that may or may not happen. But I wouldn’t expect the task force to issue a formal position on the paper. It is what it is. It’s a piece of the puzzle.
Could you clarify what your own views are regarding frequency of vaccination and risk of tumor?
There’s never really been a study to look at the relative risk of annual vaccination versus vaccination every three years on tumor development, probably because, in part, vaccination every three years is something that’s relatively new to veterinary medicine. My feeling is that there is a subset of genetically predisposed cats that get these tumors, and I don’t know if they would get them less frequently if they were vaccinated every three years than if they were vaccinated every year. But based on the research that other people have conducted, my sense is that in most cases I would support the recommendations of giving vaccines every three years instead of annually. It’s possible that it might decrease the incidence of these tumors. It’s possible that it might not. If a cat is going to get these tumors through a vaccine regardless of how frequently it’s given, then it might not make a difference.
What kind of studies are necessary to further quantify the role of genetic predisposition?
That’s going to take genetic studies where people can actually find markers, genetic markers of cats that are at higher risk of getting these tumors. Those aren’t the sorts of studies that I do, but I think ultimately that’s what will be necessary in order to really identify what the subset of the population is that gets these tumors or is at risk of getting them.
I would say that there’s still a great deal that we don’t know about this problem. Additional work is going to have to go in two directions. One is the genetic predisposition connection. And the other is to continue to do population-based studies, because different vaccines come out over time. It’s possible that new vaccines may be either equivalent, worse, or better in terms of the ability to induce tumors. So I don’t think genetics is the entire problem. Like vaccines, I think it’s just part of it. That’s why we need more of both kinds of studies.