A series of immunizations is required for a young pet to develop its immunity. The immune system of newborn puppies and kittens is immature. For that reason, the newborn receives immunity called antibodies from its mother through the milk it nurses for the first 24 hours after birth. This “special” milk is called colostrum. These antibodies are called passive immunity and exist for varying periods of time in each individual young pet. In some pets, this immunity may last up to 20 weeks of age, while in others it may last only a few days or weeks. The problem for the doctor is there is no easy, practical way to measure how much of this passive immunity is present in each pet –and how long it will last.
Vaccinations contain antigens which have the capability of causing the pet’s own immune system to produce its own antibodies. This is termed active immunity. However for the vaccination to be able to cause this stimulation, the pet’s body must have very low levels remaining of the passive immunity it got from its mother. When a vaccine antigen is administered to a pet, that antigen has the ability to stimulate immunity for only 5 days or so. If the passive immunity remaining from the mother’s milk does not drop low enough for the vaccine to “over-ride” this obstacle, the vaccine will not work and loses its potential strength to do so in approximately 5 days.
It is also possible that the pet’s overall condition may not be sufficient to allow the immune system to work at its optimum level. Malnutrition and parasites can greatly reduce the body’s ability to produce its own active immunity. Since there is no quick, inexpensive way to measure this passive immunity level, a series of vaccines must be given to be sure there is active stimulation present when the pet’s body is able to do it. As mentioned before, this particular time varies from pet to pet. This series of vaccinations must be spaced out so as to allow a minimal “window of opportunity” for disease to occur. This “window of opportunity” is defined as the time when the passive immunity (from the mother’s milk) is too low to protect the pet from disease, and the time when a vaccine antigen is available to stimulate the pet’s immune system.
It should also be noted that a very small percentage of pets do not have an immune system capable of producing immunity at any age. This is similar to the kids that must live in a “plastic bubble.” They have the same problem. They have a body much more susceptible to disease since their immune system does not work normally.
Your own veterinarian, considering age of the pet, breed, environment, overall health, and disease prevalence in the area, must determine the particular vaccination program, including specific vaccinations used and frequency of administration.
YOUR PET IS AT RISK UNTIL THE ENTIRE SERIES OF VACCINATIONS IS COMPLETED:
• Follow the individual vaccination schedule for your pet recommended by your veterinarian.
• Be sure to return on time to minimize the pet’s “window of opportunity.”
• For more information on feline vaccines please see FELINE VACCINATIONS.
• For more information on canine vaccines please see CANINE VACCINATIONS.