Vaccines, as I have mentioned many times on this blog, are perennially controversial. Many people worry that pets are vaccinated too often. Experts voice concerns that over vaccination may lead to autoimmune disease. Leukemia and rabies vaccines in cats have been linked to cancers at the injection sites.

The obvious goal for every veterinarian and conscientious pet owner should be to vaccinate pets neither too frequently nor too rarely. In an ideal world, we would vaccinate pets exactly as often as necessary. I predict that in the future this will be the norm. But as of 2009, it is impossible to say how often pets need vaccinations.

Some facts are clear. Juveniles (puppies and kittens) need vaccines more often than adults. Animals with different lifestyles need different vaccination protocols. And most important, every individual responds differently to vaccines. Every individual therefore has unique needs.

Measuring those needs is impossible. Blood tests called titers give some idea of a pet’s response to previous vaccinations, but titers measure only half of the picture. Titers measure antibody levels in the blood. However, antibodies cannot function without another component of the immune system called cell-mediated immunity. At this time there is no way to measure cell-mediated immunity. Therefore there is no way to measure a pet’s true level of immunity to disease.

I agree that many pets are vaccinated more often than necessary. On several instances I have treated animals for autoimmune disease and wondered whether vaccines might have contributed to the problem.

However, on hundreds of instances I have treated canine parvovirus. In every single one of these cases I knew with certainty that vaccination would have prevented the problem. I never have treated a properly vaccinated dog for parvo. The vaccine works.

I euthanized a 12-week-old puppy today because of parvo. A vaccine could have saved his life if it had been administered at the right time.

Over vaccination is a bad thing. Veterinarians and pet owners should work to prevent it. But don’t forget that under vaccination is even worse.

Your best option as a pet owner is to find a good vet who will take the time to discuss the controversies surrounding vaccines. Tailor a vaccination protocol to your pet based upon his or her needs, age, and lifestyle.