Why a 1 year vaccine?

There are a few vaccines that we deem as "core" vaccines that are highly recommended in cats.  One in particular is a vaccine against the rabies virus.  Fortunately, in most area of the United States (Illinois included), rabies is not a huge problem and only few cases of rabid animals and very rare cases of human exposures are reported.  One of the main reasons for this is the implementation of rabies vaccines in our pet population, who can be carriers and propagators of the disease.  In areas were mandatory rabies vaccination of pets and wild dogs is not required (such as India) rabies is a huge problem with over 20,000 people killed each year.



You may say that my cat is indoor only, so I don't think they need to be vaccinated as they won't be exposed to any other potential carriers of the disease.  This may be true, but in our area the most common carrier of the virus are bats, which on occasion to get in the house and may cause exposure to your pet.  Because of this, the public health concern, and the fact that County laws requires it, we highly recommend that your cat be vaccinated against rabies.

Okay, now that we have decided that we should vaccinate your cat for rabies, what is the best vaccine to use?  There are a few vaccines available that are effective in protecting your cat from rabies.  The one that we recommend is the Merial PureVax vaccine.  This uses a recombinant canarypox-vectored vaccine technology.  Basically what that means is they take little snipets of the rabies virus' DNA and implant them into the DNA of a canarypox virus.  Once this is injected under the skin, your cat's body recognizes the canarypox virus as a foreign virus, so mounts an immune system response to fight off the virus.  In doing so, the body also mounts a response to the snipets of the rabies DNA, which gives your cat protection against rabies.  We rarely see side effects to the virus and are very happy with the results.  The one downside to this vaccine is that it is only labeled for protection for 1 year, so has to be boosted annually (as County laws are strict about following the labeled protection).



Why do we use the 1 year vaccine over available 3 year vaccines?  The main reason that we do this is safety.  In the late 90's and early 2000's, the veterinarian community noticed an uptick in aggressive skin tumors call fibrosarcomas.  When looking at cats with these tumors they noticed that many of them were occurring over the shoulder blades where most vaccines were previously given (lots of loose skin here that made for easy administration).  Pathologists looking at these tumors under the microscope also noticed that they saw some foreign material that could be associated with previous vaccines.  Many vaccines use a slightly different technology for vaccines where a portion of killed virus is added with an adjuvant and injected under the skin.  The adjuvant is a caustic substance (usually not disclosed by the vaccine maker) that is meant to stimulate the immune system to react and subsequently react to the killed virus (which is typically too weak to stimulate the immune system itself).  It was hypothesized that the adjuvant was doing such a good job that it caused chronic inflammation in these areas that eventually would end up transforming into cancerous cells.



Planning for removal of large tumor on the back.

 These tumors are very aggressive and tend to metastasize (spread to other organs like the lungs) readily and without extensive surgery (sometimes removing parts of the scapular bones or chest wall) tend to grow back quickly (as soon as 2-3 months).  Even with extensive surgery these tumors can recur or spread and many cats don't make it longer than 1.5-2 years after they are diagnosed.

A cat after removal of a vaccine associated fibrosarcoma

In response to these tumors, a company switched to the canarypox vaccines and we have seen a declined in these tumors.  Because of a problem with a control group during testing of the vaccine, the vaccine was unfortunately denied a 3 year label, so we are stuck with the 1 year vaccine for the time being.  However, the safety of the vaccine (in my opinion) outweighs the inconvenience that may come with a 1 year vaccine.

Please let me know if you have any questions.