The Puppy Immune System - Why So Many Vaccines?


Puppies are always growing, always active, and always changing. Most of the changes occur as we watch them visibly, but a lot happens "inside" that we can't see. A good example of this is a puppy's immune system and the challenges it faces as it develops into a healthy system capable of protecting the puppy against some serious and potentially life threatening diseases.

The greatest challenge in protecting a puppy against infection has to do with the natural mechanism of "maternal immunity". It is obtained from the puppies' mother as an extension of her vaccine antibodies (obtained during appropriate vaccination throughout her lifetime). This initial puppy immune system is passed from the mother dog to the puppy via "Colustrum" (Mother's Milk) when the puppy nurses on its first day of life. This milk contains important antibodies against parvovirus and many diseases and until these antibodies wane to ineffective levels, they will protect the puppy.

Challenge I: Natural immunity can also inactivate puppy vaccines

Vaccines are a solution of inactivated virus either live, weakened (alternated or modified) or killed. The vaccine (virus) is injected into the puppy to stimulate the immune system. If the pup's immune system still has adequate maternal antibodies, this vaccine may be inactivated just as if it were fighting a real infection. There will be a period of about a week when there is not enough maternal antibody to protect the puppy but too much to allow a vaccine to work. After this "window of vulnerability" period, vaccines will be effective.

We must understand that after a puppy is born maternal antibody levels drop by about half every 10 days. Pups born first or those most aggressive at nursing on the 1st day of life will get more maternal antibodies than their litter-mates. Mother dogs vaccinated just prior to breeding will have the highest antibody levels to pass to their puppies. In this case maternal immunity interference will last longer in contrast to a poorly vaccinated mother dog, a "poor" nurser puppy or maybe the "runt" or last pup born in a litter.

Challenge II: The age at which vaccines can be effective is different for each puppy 

To get around this, we vaccinate puppies in a series - giving a "Distemper-Parvo" vaccine every 3-4 weeks starting around 8 weeks of age until the puppy reaches 16 weeks of age. By age 16 weeks, we can be assured that maternal antibodies have waned and that vaccinations will be effective. When the puppy's own immune system boosts - that is, when it will be a healthy one - it's capable of protecting the puppy against diseases such as distemper, adenovirus, parainfluenza, parvovirus, etc. 

Although the puppy immune system is not a simple one, one thing is simple - giving your puppy the best start in life begins with vaccinations and physical examinations from your veterinarian to monitor health progress. It's the best insurance you can buy to protect your loved one for many happy years to come!

By Dr. Maribeth Hartwick