How Vaccines Work & the Risks of Too Much of a Good Thing


I read your column regularly and respect your advice. What do you think about this perspective? Summary of News Article: Are We Overvaccinating Our Pets? You may get notices from the veterinarian every year or two suggesting you revaccinate your pet for distemper, leukemia or other diseases. But now some vets are wondering whether the repeated doses can do more harm than good.


Dr. Nichol:

Your question is timely. In the last few weeks most of us have gotten more cautious. It seems like any protection is good and more is better. So if there’s a vaccine against it, we want it now and we want it often. But repeating it every year may create other trouble.


Protection against rabies and distemper is essential. Other diseases like leukemia in cats or corona virus in dogs are potentially deadly; but it may not be a good idea to vaccinate every pet. More isn’t always better.


We’ve come a long way. In the early days, vaccination meant literally giving a mild case of the disease itself. If the person or critter survived, their immune system would respond by making antibodies that could fit neatly onto the offending virus. If those sneaky buggers came back for a second strike, the antibodies would rip them apart.


Eventually, researchers learned they could replicate a virus, through several generations, and end up with a similar but distantly related cousin. These guys won’t make anybody sick-but they’re still a close enough match to stimulate neutralizing antibodies. Isn’t history fun?


Modern vaccinations are much safer, but they aren’t 100% risk free. To help make them effective, the manufacturing labs use small amounts of modified virus but add punch to the mix with helpers called adjuvants. These chemicals seem OK in the lab. But if they’re overused, they may cause problems ranging from cancers to foul-ups in the immune system. Even low thyroid function may result from too many vaccinations.


It sounds like modern medicine run amok. In reality very few pets have problems. Still there is much current research on reducing the frequency of vaccines. While puppies and kittens need a series of 2-3 as babies, not all adult pets need annual boosters. Reduced vaccination schedules have already been approved for cats and lower frequency recommendations for dogs are expected soon. Ask your veterinarian for the latest or stay tuned right here.