Can Vaccines Cause Cancer in Dogs?

The evidence says no (beyond the rare injection-site sarcoma). But I'm willing to engage in debate.

dogedit  |  Oct 9th 2012

I recently received a question from a fellow Dogster writer:

Hi Eric,

More than a few commenters on my cancer story are claiming vaccines cause cancer. It would be great if you could weigh in with your professional opinion.



The timing of this qustion could not have been more apt, because I had just finished writing an article for Catster on injection-site sarcomas (formerly known as vaccination-associated sarcomas) in cats. The link between vaccines (and other injections) and cat cancers is well-known and well-proven. In dogs, the matter is much muddier.

A recent paper in the Journal of the American Veterinary Medical Association stated that vaccines have been linked to injection-site sarcomas in dogs. These tumors appear to be dramatically rarer in dogs than in cats (and they’re already quite rare in cats), but they have been reported. To put things in perspective, I’ve never seen one, and I’ve never met a vet who has.

But do vaccines cause other types of cancers in dogs? I have heard some vets posit that today’s seemingly increased rates of cancers such as lymphoma may be linked to over-vaccination. And I have heard, ad nauseum, plenty of screaming anti-vaccination fanatics claim that vaccines cause all manner of harm in all kinds of species. In these types of situations, I always invoke the modified Jerry Maguire rule: Show me the study!

And that’s where the claims linking vaccines to cancer (other than extremely rare injection-site sarcomas) fall short. I have searched veterinary databases repeatedly — I did a search just today — and have yet to find a study that links canine vaccinations to other types of cancers. If any person reading this can site such a study, I’d be very interested to read it. Note that I’m not interested in reading anti-vaccine propaganda. I’m interested in controlled, well-run scientific studies.

It is noteworthy that when one searches veterinary databases for studies on vaccines and cancer, many results do appear. But they do not describe studies showing that vaccines cause cancer in dogs. Rather, they are papers reporting on the use of vaccines to treat cancer.

Vaccines are designed to stimulate the immune system, and it turns out that the immune system can be activated to fight cancer in the body with special vaccines. A vaccine for treating certain canine melanomas is already available. Researchers also are exploring vaccines to treat lymphoma, mammary tumors, and soft tissue sarcomas.

This article should not be construed as advocacy for an every-shot-for-every-dog-every-year policy. Quite the contrary. Whether or not over-vaccination causes harm, administering unnecessary vaccines to dogs does them no good. The truth is that nobody knows how often dogs should be vaccinated. Each dog’s needs are unique. Some people advocate using blood tests known as titers to determine whether dogs need to be vaccinated. Titers do provide useful information, but they only measure half of the immune system (they measure humoral immunity, but ignore cell-mediated immunity).

Most well-respected veterinary institutions now generally recommend triennial vaccination for most dogs. For older dogs, I think that might be overkill. My pal Buster most recently had vaccines two-and-a-half years ago. He’ll definitely get his rabies vaccine when it’s due in six months, since it’s required by law. But, at eight years old, I’m not sure I’ll be giving him any others for a while longer.

Further research on vaccination protocols is highly warranted. An honest, well-informed public discussion about vaccines is a very good thing. And people shouldn’t lose perspective: Unvaccinated dogs die from parvo every day. There is no question that, on the whole, vaccines save lives. Every puppy should benefit from a full set of vaccines. Every pet owner should talk with their vet every year about which vaccines, if any, might be appropriate.

Unfortunately, well-informed public discussions about vaccines are very difficult to have. The discussions often are hijacked by anti-vaccination fanatics. These folks seem to believe that vaccines are the cause of all the world’s problems. They spend an awful lot of time on the Internet, and they love to comment on articles like this one. They tend to grasp onto any evidence (no matter how spurious) that vaccines might be dangerous, and they are fond of linking to propagandist websites that promote their cause. In my opinion, they don’t contribute anything useful to the conversation.

Don’t get me wrong. I want to listen to people who have had bad experiences with vaccines. I want to evaluate any solid evidence put forth in favor of or against vaccines. But I don’t want to hear propaganda.

If you feel that you have something productive to add to an honest, well-informed public discussion about canine vaccination, please dive into the comments section.

Or, you can take this poll: Readers, have you ever had a bad experience with dogs and vaccines?