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The Importance of Booster Vaccinations

Randy Walker DVM

About Booster Vaccinations...

Most vaccinations we give require boosters. For puppies we give the initial. distemper/parvo vaccination at 6 weeks and then booster this vaccination at 9, 12, 15, and 18 weeks of age followed by a yearly booster thereafter. For kittens we give an initial distemper vaccination at 6 weeks of age followed by the feline distemper booster and initial feline leukemia vaccination at 9 weeks. The feline leukemia vaccination is then boostered at 12 weeks along with yearly boosters for both feline distemper or and feline leukemia thereafter. The rabies vaccination gets a booster one year after the initial injection and then every 3rd year thereafter for both dogs and cats.

My Puppy Or Kitten Has Received An Initial Distemper Vaccination. Why Should My Pet Need To Complete The Booster Series In Addition To This?

There are two main reasons why the boosters in the puppy or kitten series are extremely important: (1) Once the immunity the puppy or kitten received from its mother begins to wear off, each booster will stimulate greater immunity in that patient. Boosters are necessary to bring the antibody level up into the highly protective range. The last injections in the series usually boost the immunity the most. (2) Shortly after birth, each puppy and kitten receives immunity (antibodies) from its mother through the first milk nursed (called passive transfer of immunity). This first milk (called colostrum) is in effect the puppy or kitten's first "vaccination". After the 1st 12-24 hours the mother stops producing this colostrum and the puppy or kitten stops absorbing it. This immunity gained from the mother through passive transfer (called maternal. antibodies) then begins to decrease in each puppy or kitten at a different rate (the antibodies get old and wear out with time just like anything else). In some puppies and kittens the amount of maternal antibodies will drop to inadequate levels as early as 6-7 weeks of age. In others the level of maternal antibodies will not drop to low levels until 10-12 weeks of age and sometimes older. If we vaccinate a puppy or kitten with a high level of maternal antibodies the vaccine will have little effect (its similar to squirting the vaccine onto a hot skillet-it gets "zapped" immediately by the "soldiers" left over from the mother's immune system) before the puppy or kitten's own immune system has time to go through the process of recognizing the disease in our vaccine and forming an immune response of its own to it.

If This Is The Case That Occasionally The First Vaccination And Initial Boosters Fail To Produce Good Immunity In Some Puppies Or Kittens Because Of Interference From The Mother's Antibodies Transferred To The Puppy Or Kitten Shortly After Birth Wouldn't It Be Best To Just Wait And Give Only The Final Boosters In The Series?

NO. All Boosters MUST be given at their proper time intervals for full protection because once the level of immunity has dropped to a certain point then the puppy or kitten is susceptible to deadly diseases such as Parvo, Distemper, Feline Leukemia, etc. This is something we absolutely cannot afford to play games with.

Can't You Tell On Physical Examination Of The Puppy Or Kitten Whether It Still Has A Good Level Of Maternal Antibodies?

No. There is no way to tell this by physical examination.

Can't You Do A Lab Test To Tell The Level Of Maternal Antibodies?

Yes, it is possible to take a blood sample to determine the level. of antibodies present to these various diseases. However this is extremely costly (hundreds of dollars), time consuming and often times unreliable. The only practical approach to vaccinating puppies and kittens in the real. world is to complete the puppy or kitten series on schedule.

What Is The Difference Between The "Regular" Vaccine And The Booster Vaccine?

They are the same vaccine. We are not exposing the puppy or kitten to a different vaccine but rather we are re-exposing the puppy or kitten to the same vaccine again in order to get a higher level of immunity.

Why Can't They Develop A "One-Shot Vaccination" That Would Eliminate The Need For These Boosters?

Its probably biologically impossible to develop a one-shot puppy or kitten vaccine where booster shots are not needed. If one were developed its unlikely that such a Monster-shot would be very difficult for a puppy or kitten's system to handle and I personally would predict serious (including fatal) reactions with such a vaccination if one existed. Gently but effectively boosting the puppy or kitten's immunity with our present vaccinations is the more prudent approach.

Does All This Mean That When It Comes To Booster Vaccinations, More Is Always Better?

NO. (This is a very good question, by the way because it brings up an important point). The booster vaccinations that we give to puppies and kittens are designed to be given every 3 weeks until the pet is 18 weeks old (that's the protocol. we use here at the clinic where I work; the specific vaccination protocol used in your area may vary). Giving the boosters at closer intervals (once-a-week or once-every-two-weeks) will result in less immunity than giving the vaccination every three weeks. This is because when we vaccinate too often and with too many things this can "confuse and befuddle" the immune system to the point that it doesn't know what to do so it basically does nothing (this is oversimplifying, of course). The better way is to wait three weeks between boosters. In this way we confront the system with our agent and force it to work to form an immune response; then we let the system rest and recuperate for a while. Then (3 weeks later) we again challenge the system to form a stronger immune response and then let it rest again for a while, etc. This gives us better immunity than giving more boosters more frequently.

Why Do You Give Yearly Boosters For The Distemper/Parvo 6-way Vaccination?

Yearly boosters are important for maintaining a proper level. Of immunity. After each booster the level of immunity will gradually drop-off so we need to booster periodically to keep the immunity up.

In My Home State Or Nation They Have Us Booster The Rabies Vaccination Every Year (Or Every Other Year). Why Is It That In Arizona You Only Have To Booster The Rabies Vaccination Every 3rd Year?

How often we booster the Rabies vaccination is set by State or local law. Since there is no scientific evidence that the dog or cat acquires any more protection from our 3-year rabies vaccination by boostering more often than every three years, the Arizona State Legislature has decided that to booster every 3rd year is adequate. Other legislatures in other states set their own requirements and in some states where rabies is more of a problem they have decided to booster more frequently.


- Randy Walker DVM
Sun Lakes Animal Clinic
May 17,2004



"Until one has loved an animal, a part of one's soul remains unawakened."
- Anatole France, 1921 Nobel Prize Speech -


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