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It’s important to understand that no vaccine is 100 percent effective all the time. Factors that can affect immune response in a puppy include his health and the level of maternal antibodies still circulating in his system. And if a puppy is exposed to a virus shortly before or at approximately the same time a vaccination is given, the vaccine is likely to fail. This occurs for any number of reasons. Some puppies simply don’t have adequate immune function. Stress, poor nutrition and other factors can interfere with immunity for short periods of time as well.
Puppies are born with some degree of natural immunity to disease, which they receive from the rich colostral milk their mother produces the first two or three days of a pups life. The colostrum contains antibodies to disease, which provide the pups with limited protection during the first few weeks of life. Called passive immunity, or sometimes maternal immunity, this protection gradually decreases and may diminish by as much as 75 percent by the time a pup is 2 weeks old. Most puppies completely lose passive immunity by the time they’re 14 to 16 weeks old.
Until it reaches a low threshold, passive immunity can interfere with immunization; the maternal antibodies destroy vaccine viruses. For this reason, puppies are given a series of vaccinations to ensure that the immune system responds to the vaccine. Otherwise, a virus can sneak in during the window of opportunity that arises when the level of maternal antibodies is low enough to make a pup susceptible to infection, yet high enough to interfere with immunization. Veterinarians generally recommend that puppies be immunized at three- to four-week intervals, beginning at 8 weeks of age and ending around 18 weeks of age. The final vaccine is the most important of the immunization series.
How frequently vaccinations should be boosted after the first series is currently a matter of discussion in the veterinary and dog-owning communities. Many veterinary schools now recommend a booster vaccine at one year of age, followed by additional boosters every three years thereafter, instead of previous recommendations of annual boosters. Some areas of the country have a higher incidence of certain infectious diseases, such as distemper and parvovirus, than others. Your veterinarian can advise you on the vaccination schedule that is appropriate for your area.
Reprinted from The Original Dog Bible © 2005. Permission granted by BowTie Press.