That was the message that Dr. Alice Wolf, an internal medicine specialist and professor of small animal medicine at Texas A&M University, delivered to a packed room of veterinarians yesterday afternoon at the 83rd Western Veterinary Conference in Las Vegas.
Vaccines with adjuvants (substances containing aluminum that are added to vaccines to increase the body’s immune response) are implicated in the development of vaccine-associated sarcomas (VAS) in cats. For any veterinarians who might still doubt that association, Wolf laid out the case. VAS were not seen before the mid- to late 1980s, when modified-live virus vaccines were removed from the market after cases of vaccine-induced rabies developed. They were replaced by killed adjuvanted vaccines, including a new one for feline leukemia virus.
The World Health Organization classifies veterinary vaccine adjuvants as a class 3 (out of 4 classes) carcinogen. Class 4 is the highest risk. If your doctor offered you a choice of two flu shots, one containing a class 3 carcinogen and one that didn’t, which one would you choose, Wolf asked the room. Why would you make a different choice for your patients?
The incidence of VAS is 1.3 in 1,000 to 1 in 10,000, up to 20,000 cats per year.
“Even one cat is too many if this is a problem we can avoid.”
Now that leads to a conundrum when it comes to rabies vaccinations. Is it better to give a cat a killed adjuvanted vaccine every three years or a nonadjuvanted recombinant vaccine annually?
“In my humble opinion, it is better to give a much less reactive product more frequently than a much more reactive product less frequently,” Wolf says.
Are modified-live and recombinant vaccines as effective as vaccines with adjuvants? Yes. Wolf cited a study by Dr. Julie Levy (the Maddie’s Professor of Shelter Medicine) at the University of Florida showing that MLV vaccines were much more effective than killed vaccines, providing earlier onset of protection and protection of more animals. The recombinant vaccine for FeLV is as efficacious as the alternative.
In her talk, titled “Feline Vaccination: Protocols, Products and Problems,” Wolf also discussed whether cats need vaccines beyond the core FVRCP (feline viral rhinotracheitis, calicivirus, panleukopenia). In most cases, the answer is no.
Worried about something called “killer calicivirus”? Don’t be. It’s not a new disease and it is rare, Wolf says. Cats at risk are those in shelters or catteries with poor husbandry.
“Virulent calici is not a disease of household pets. All virulent isolates are different, so a single stable vaccine strain isn’t going to protect against all the mutations out there. That’s why the vaccine isn’t useful. Your patients don’t need it.”
To avoid spreading virulent calici (or any infectious disease), Wolf advises veterinarians not to admit sick shelter cats to their hospitals and to use strict disinfection, isolation and hygiene procedures for any animal suspected of having a contagious disease.
“If you have good protocols in place, you don’t have to worry about sneezing cats, coughing dogs and puppies with diarrhea.”
The vaccine for FeLV is universally recommended for kittens because they are most susceptible to the disease. Older cats are much more resistant to the disease. After kittenhood, assess the cat’s risk based on whether and how often he goes outside.
Which vaccines should cats not receive? Wolf enumerated those with little or no efficacy: giardia, feline infectious peritonitis, feline immunodeficiency virus, virulent calicivirus, and bordetella. Don’t give them to cats.
Photo credit: Feline vaccination, flickr Creative Commons (Feral Indeed)
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