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Merial Limited has just released its new feline leukemia vaccine called Purevax Recombinant Leukemia Vaccine.  This is the first veterinary vaccine to be delivered via the VetJet transdermal vaccination system. The VetJet system uses a spring device to deliver a tiny amount of vaccine through the skin into the dermis itself, a layer of skin just under the epidermis, rather than into the deeper subcutaneous space. By using this dermal space, the vaccine directly targets the Antigen Presenting Cells, the very cells needed to start the immune process.

The new FeLV vaccine is non-adjuvanted, which means that it contains no aluminum or other adjuvants added to enhance the patient’s response to the vaccine.  Adjuvants are used to keep the vaccine product in the patient’s system longer so that the immune system can “see” the antigens longer and build a bigger response to them.  These adjuvants, however, have been linked to chronic inflammation, vaccine reactions, and even tumor formation.  The Purevax Recombinant Leukemia Vaccine, instead of using adjuvant, uses recombinant technology to amplify the patient response.  It uses canarypox virus (a virus that cannot replicate in mammals) to amplify a piece of the leukemia virus, not even the entire virus.


Fort Dodge has introduced a new vaccine for feline immunodeficiency virus (FIV).  This is one of the immunosuppressive viruses which affect cats, similar to feline leukemia virus (FeLV).  While this may sound like a good thing for cats, it is a mixed blessing.  Most veterinarians recommend routine testing of all cats for FeLV and FIV at least once in their lives.  These tests usually are run in the office as a combination test.  Standard viral tests usually look for either the virus itself (antigen) or evidence of the virus (antibody).  A normal immune system will make antibodies to antigens (viruses, bacteria, foreign proteins, even vaccines) which invade the body.  These antibodies can last years after the body has been exposed to the invader.  The presence of antibodies does not necessarily mean that disease currently is present – just that the animal has been exposed to the antigens or invaders (or vaccine).

This is the crux of the problem with the new FIV vaccine.  Current testing for FIV consists only of an antibody test. So any FIV-vaccinated cat will test positive on a screening test for FIV.  If large numbers of owners elect to have their cats vaccinated and if the cats become strays and are found, new owners will take them to vets for routine screening and they will be positive.  It is not possible to tell a cat which really has FIV infection from a cat merely vaccinated for the virus. The cat may be euthanized because the owners think the cat has FIV when he really only has been vaccinated. This is not the case with FeLV vaccinations because the test for FeLV is an antigen test which actually looks for the virus itself.

Does the vaccine have a use?  There certainly are situations where the vaccine can be very useful.  You need to discuss your situation with your veterinarian.