Pet Vaccines 104 - How Often Should You Vaccinate?

Try these links for previous articles in the series on canine vaccines, feline vaccines, and how vaccines work.

You've probably had many vaccines yourself - vaccines for measles, mumps, hepatitis, tetanus and more. And if you're like me, you're likely hard pressed to remember what you've had and when... but you probably remember several sore arms spaced throughout life. Every vaccine varies in effectiveness and duration, meaning sometimes you need a vaccine once (measels), annually (flu), or every several years (tetanus). This article will attempt to demystify some of the when of vaccines for your dog and cat.

The Vaccine Schedule
For those who just wandered by looking for the recommended vaccine schedule without a burning need for the why behind those recommendations, let's get it out of the way:

• Puppies 
• Distemper, Hepatits, Parvovirus (DAP): every 3-4 weeks, from 6-16 weeks old
• Rabies: once at 12-16 weeks
• Bordetella (optional, but recommended for puppies): intranasal once at first vaccine appointment
• Leptospirosis (optional, recommended in most areas): at 12 and 16 weeks
• Kittens
• Herpes, Calicivirus, Panleukopenia (FVRCP): every 3-4 weeks, from 6-16 weeks old
• Rabies: once at 12-16 weeks
• Feline Leukemia (FeLV) (optional, recommended for kittens): at 8 and 12 weeks
• Adult Dogs & Cats with initial and regular vaccination history
• DAP or FVRCP: every three years
• Rabies: every three years (some states/municipalities require annual vaccination, however)
• Bordetella and leptospirosis (dogs), FeLV (cats): Annual if indicated

Why Are Puppies and Kittens Different?

Right after birth some "magic" happens inside mom and her kids - and by magic, I mean really complicated physiological changes. These allow antibodies (proteins that help prevent infection) from the mother to exuded in her milk, and for a brief period the pups or kittens can absorb these antibodies through the gut and into the bloodstream. These maternal antibodies hang around for the first six weeks or so and protect them from common diseases - that's why we generally wait until after six weeks to begin vaccinations.

Eventually those maternal antibodies start to break down, however, leaving the kids increasingly susceptible to disease. So, we start vaccinating them to teach their own  immune system how to protect itself. There's a hitch, though: the remaining maternal antibodies interfere with those vaccines and prevent the pet from developing a full immune response until they are gone. Somewhere around 12-14 weeks the maternal antibodies should have entirely disappeared, and that's why we booster most vaccines every 3-4 weeks until then - each vaccine gives the immune system a boost that keeps the pet safe, but that boost doesn't "stick" until mom's antibodies get out of the way. It's also why we don't give rabies vaccines until after 12 weeks.

Why Do Some Vaccines Need A Second "Booster?"
Some vaccines are more effective at stimulating the immune system than others; for example, a single dose of rabies will typically provide immunity for at least a year. Others, like leptospirosis, pack less of a punch; for those the first shot "warms up" the immune system so it's ready to mount a full response when boosted 3-4 weeks later. The reasons for this mostly have to do with the type of vaccine in question (see the previous article) and are beyond the scope of this article - trust your vet to sort this out for you, or ask them for the details when you've had six or more cups of coffee.

Wait, I Thought Fluffy Needed Shots Every Year?
How long is a vaccine good for? It's an easy enough question to answer - if you're willing to spend the money and time to vaccinate a bunch of animals, then maintain them in a controlled environment monitoring their immune response. The vaccine companies did this, of course, but generally just for a year. So, we knew the vaccines were good for at least that long but really didn't know when immunity started to fade, and thus when a booster vaccine was really necessary. At the time, recommending annual boosters made perfect sense as the safest thing for pets.

We now know, however, that most of the "core" vaccines generally provide good immunity for three years or longer, and most of us have changed our recommendations to reflect that. So, why so some veterinarians still hang on to the old annual recommendations? Maybe you're tempted to think it's about money - that vets see yearly dollar signs associated with yearly vaccines. That couldn't be further from the truth - after all, if money was our focus we'd all have become human physicians instead, doing essentially the same work on a different animal for three times the income. No, the reason many vets still recommend annual vaccinations is because it's a reliable way to get you to bring your pet to the clinic for the most important part of the annual visit - the physical exam.

This bladder stone - which basically filled the entire
bladder - was discovered on "routine" physical exam.
The owners had no idea the dog was having urinary issues.

It's no secret most people associate going to the vet with "getting muffy's shots," not "getting a physical." And yeah, you likely don't take yourself in for a physical yearly, either. The trouble is you know when your tooth hurts, when you've been nauseous for a month, or when your knees are starting to feel sore in the morning. You can get in the car and head to the doc as needed, or at least tell someone what's wrong and ask for a ride. Our pets don't have that luxury. Sure, sometimes it's obvious Muffy isn't feeling well - but ask yourself, do your friends and family notice every time you're not feeling well? And how long does it take them if they do notice. I couldn't tell you how often I find problems a pets' people had no idea about - everything from bum knees and ear infections, to bladder stones and broken teeth. Regular physical exams are hands-down the most essential service your vet offers, and while I don't agree with recommending vaccination more frequently than necessary to get pets in the door for that exam, I certainly understand why some vets still do it.

Note that several vaccines - leptospirosis, feline leukemia, bordetella, and lyme to name a few - don't last as long and really do need annual boosters. And for any vaccine, I always recommend a booster at one year the first time a pet receives it, regardless of the potential duration. Better safe than sorry (or stuck in the ICU with parvo). Our final article will cover adverse vaccine reactions; these are understandably a major concern of many folks, but fortunately are fairly rare.