The length and timing of the window of susceptibility is different in every litter, and even between individuals in a litter. A study of a cross section of different puppies showed that the age at which they were able to respond to a vaccine and develop protection (become immunized) covered a wide period of time. At six weeks of age 25% of the puppies could be immunized. At 9 weeks 40% of the puppies were able to respond to the vaccine. The number increased to 60% by 16 weeks, and by 18 weeks 95 % of the puppies could be immunized.
Almost all researchers agree that for puppies and kittens we need to give at least three combination vaccinations and repeat these at one year of age.
Drs. Foster and Smith prefer to vaccinate puppies with a combination vaccine at six weeks of age initially, with boosters given every three weeks until the puppy is about sixteen weeks of age. We feel that this schedule will help protect the widest range of dogs. We realize that with our protocol we will be vaccinating some dogs that are not capable of responding and we will be revaccinating some dogs that have already responded and developed a protection. But without doing an individual test on each puppy, it is impossible to determine when the puppy's immune system will be best able to respond. We also realize that in the face of an infection, due to the window of susceptibility some litters will contract a disease (e.g., parvo) despite being vaccinated. By using quality vaccines and an aggressive vaccination protocol we can make this window of susceptibility as small as possible. Our vaccination protocol may not be right for every puppy. Puppies that are not exposed to other dogs and have a very small chance of coming in contact with parvovirus may not need to be vaccinated as frequently. At the same time some 'high risk' puppies may need a more intense and aggressive vaccination program. It is best to work with your veterinarian on a vaccination protocol that is best for your individual puppy or kennel, taking into consideration your individual situation.
