Vancouver Feline Hospital - Cat Veterinary Clinic

FELINE VACCINES: An unbiased approach?

Vaccines have played the most important role in the prevention, eradication and control of disease. Their value in population medicine and individual health is proven, but often ignored in the furor of current controversy. We have perhaps forgotten the severity and tragedy of the diseases they prevent, or the enormous cost in terms of lives other methods of disease control can exert (remember Foot and Mouth, UK, 2001?).

This does not mean we should blindly apply a blanket approach to all vaccines. Not all vaccines are the same. Vaccine efficacy and value depends on the strain used, the way the organism has been inactivated or modified, the response of the individual immune system, the handling and storage of the vaccine, the actual risk-benefit ratio of the vaccine, the cost of the vaccine versus the economic cost of the disease and its sequlae, and how many in the population need to be vaccinated.

Parasites and disease evolve with their hosts. Mutations cause new strains of viruses or better parasites or "superbugs", some of which can "jump" species. Not all of these mutations are lethal or cause massive outbreaks of debilitating disease. Over time, we adapt. The immune system is capable of responding to a challenge quite quickly. Successful parasites evolve ways to avoid or use the immune response to their best advantage. Our lifestyles can severely affect our immune capabilities.

The bad diseases are the ones that kill or severely maim. Medicine's worst enemies have traditionally been those that affect the young, although the trend now is towards those that affect the population that can pay for the remedy. So vaccines were developed for diseases that kill the kittens - the upper respiratory diseases and panleukopenia.

In the western world, we don't see those kittens anymore - those daily tiny tragedies of new life snuffed out with unremitting suffering or the chronically ill survivors, spraying snot globs wherever they went, which was never very far because of the residual lung disease. Spaying and neutering, decent nutrition, and vaccination have increased the average lifespan of the domestic cat from 2 years to 12 years. We expect our household cats to live over the age of twenty now. "Old" has new meaning for a cat because they now experience middle-age.

Depends where you live, of course. On you, the owner. To some extent the genetics of the cat.

Vaccines are important. They do their good. Do they do harm?

Adverse events can occur, as with any substance. How often they occur and what the actual harm done is more relevant. This can be tricky to find out. Medical studies, rigorous scientific studies or the other kind, are always fraught with contradictions -studies may be repeated and results may be different, devaluing the previous study and promoting a fad cycle. This may happen because we are running experiments in a complex biological system we do not fully understand, trying to control the results in an artificial environment and make the human error of assuming our experience is the only relevant one. This is true when logging adverse events. Doctors don't like it when they give something that caused harm to their patients. One bad experience and they will never use the product again, and will do their best to influence their colleagues the same way. (This happens the other way too; a subjectively good experience may be lauded as the next cure and become common practice). Knowledge evolves in this roundabout way, much like a parasite-host relationship.

Today, the individual and not the population's benefit is more important for many diseases - the vaccination against that particular disease may have switched roles from a public health benefit (harm one for the good of many) to an individual benefit (does the individual's risk justify this?). E.coli vaccine in feedlot cattle will be an example of an animal vaccine given to that entire population for public health benefit. Smallpox vaccine seems to have changed roles from being given to every individual, to being available for only those at risk and lucky enough to have access to the vaccine. Feline leukaemia vaccine is one that is given for only individual benefit.

A thorough understanding of the disease or new technology may be needed to develop a vaccine that works. Just because there is a vaccine on the market does not imply efficacious prevention or that it must be used in every individual.

I give vaccines, lots of them, every day. I have received vaccines, lots of them, especially in my childhood. Today, I choose the vaccines with care, asking those cynical questions, and doing my very best as a doctor not to cause harm, in the light of current knowledge. I advocate a specific vaccination because, to my knowledge, the benefit of that vaccine far outweighs the risk.