The 2 Perceived Risks of Overvaccination in Pets

"The question you ask about risk and vaccination, especially in today's environment, is really a good question," says Richard Ford, DVM, MS, professor emeritus at North Carolina State University College of Veterinary Medicine. "It's highly relevant to everybody practicing. And let me say there are 2 perceived risks, the first one is, 'Oh my gosh, we're giving so many vaccines we're going to overwhelm the immune system and the risk is the patient won't be immunized by the vaccines given, because we've just given so much.' And that is myth, that does not happen. The immune system is incredibly capable of creating an immune response to many more antigens than we can put into vaccines right now, so that's a given.

The second risk, and I think the one that you're driving at with your question, is the risk of injury caused by vaccines. None of us want to do that but we're using biological products that in fact can induce injury. The numbers are low, to the point they're rare, but they do occur and it’s not always predictable when it’s going to occur.

If an animal is allergic they are usually allergic to one of the constituents in the vaccine not the immunizing proteins themselves, its the other stuff in it. And so, the issue of concern is how do you mitigate the risk and since you can't predict it what you can do is there's some common-sense recommendations, which is small dogs, small breed dogs, getting lots of vaccine at the same appointment are at highest risk. I think we knew that intuitively but there's a study that shows that's true, and so, we're saying when you get to the 20-pound dog and under, this is 20 pounds at its estimated adult weight, the risks start going up when you're giving multiple doses of vaccine at one appointment, and we are recommending don't do that. Give them the core vaccines then later, at a time when its convenient for the client and the veterinarian and everybody's happy, give these non-core vaccines. And the obvious example is a 4- to 6-pound dog you want to give a non-lepto, or Lyme vaccine all by itself. You just don't want to load them up with a lot of vaccine at the same time. There is a recommended interval and we would like veterinarians to, when they're separating doses of vaccines, number one, it should be a minimum interval of 2 weeks between doses of vaccine. Actually, in humans they recommend three weeks and in some cases 4 weeks depending on the vaccine. We generally recommend three to four weeks interval, absolutely not less than 2 weeks, and that's to ensure a good immune response to the vaccine.

But other than that, there's no real contingent, other than, to address your question most veterinarians know we don't like vaccine administered prior to about 6 weeks of age, that would be the absolute earliest recommendation."