I’ve heard a lot of people say that they refuse to vaccinate their cats because it will give them cancer (sarcomas?). Is that a real thing? When I google it is really hard to sort through what’s anti vax and what’s properly researched info.
gettingvetted here.
With standard rabies and feline leukemia vaccines (the two killed vaccines that are available for cats) there is a chance of vaccine site sarcoma. These cancers are extremely aggressive, grow very quickly, and tend to have "octopus tentacles" that reach farther and deeper than the main bulk of the tumor. It is extremely difficult to remove them because you have to remove them with a very wide margin which usually includes taking muscle or other tissue under the mass, and they are very likely to recur. This is why most vets today will vaccinate as far down on the limbs or even the tail as possible, because it is much easier to amputate a limb or tail than to remove such a large and aggressive tumor from between the shoulder blades (the previous favorite location for all vaccine injections).
However, the development of this cancer is a 1 in 10,000 lifetime chance. As a result, it is very hard to study these cancers in a controlled setting, because you would need to keep 10,000 cats for their entire lives, hoping to see one case of cancer. It is hypothesized that the adjuvants (additives/irritants) which are necessary to get the immune system to respond to a killed vaccine (why would the immune system react to something already dead?) are responsible for the cancers. For some reason, cats respond negatively to any kind of inflammation - resorbing their own teeth just because they have a little gingivitis, going into liver failure just because it was a little overworked when they didn't eat for a couple of days, and cancer at the site of certain vaccines. Today there are newer killed vaccines that use fewer adjuvants and different adjuvants than historical vaccines. Obviously since the risk was already extremely low, it is hard to track real-life instances and prevalence of this cancer. But, at this time, there are no recorded instances of vaccine site sarcoma if a cat has only had these modified vaccines during their lifetime.
Regardless of which vaccine is used, in the US it is legally required to have an up-to-date rabies vaccine in most states, and the risk of rabies (and feline leukemia in outdoor cats) is higher than the risk of cancer. Vaccine site sarcomas should not be a reason not to vaccinate, especially since we have safer alternative vaccines available.
**note - the FVRCP ("respiratory") vaccine for cats is a modified live vaccine which doesn't require significant adjuvants and vaccine site sarcomas have not been associated with this vaccine.
