One of the most common things that I do in veterinary practice is to administer vaccinations to animals. Since we are just starting out, I thought that you might want to know the answer to a question that many people think and few ask.
"Doc, why does my dog need so many puppy shots?" It's not because we like to sell vaccine. It's not because we want to make puppies mad at us every four weeks for the first 16 weeks of their lives. Rather, it's to protect them from potentially deadly diseases.
Dogs and cats are protected from certain diseases in the first weeks of life by a process called "passive immunity". As animals grow and their own immune system develops, they are protected by "Active Immunity". Passive immunity is the protection transferred to a baby from it's mother. This protection is in the form of proteins (called antibodies) made by the mother's immune system. Small amounts of protective antibodies are given from mother to baby through the placenta during gestation. However, most maternal antibodies are transferred from the mother's first milk (colostrum) to the newborn intestine and into the babies' blood during the first few days of life. The intestinal tract only absorbs maternal antibodies for 48 to 72 hours. This emphasizes the importance of getting mother's milk in newborn animals soon after birth. The dilemma is this! Passive immunity only protects newborn animals for a period of time. There is a window of time between eight and twelve weeks of age when maternal antibodies decrease in concentration, but their presence prevents the animal's immune system from responding to vaccinations. Vaccination protocols focus around this window. Because there is no cost effective way to know when maternal antibodies are reduced enough for the animal's immune system to respond to vaccination, we typically vaccinate dogs and cats at 6-8, 12, and 16 weeks of age. High risk breeds are often boostered at 18 to 22 weeks old.
Active immunity is the immune system's response to challenge by infection or by vaccination. It takes seven to fourteen days for the immune system to respond after initial exposure to an offending virus or bacteria. If an animal had previous exposure (ie. vaccination or disease), the immune system would respond more quickly and stronger, thus protecting the animal soon after exposure. Your animal gets a series of vaccinations because the "window of susceptibility" is several weeks long. This window is the time that there is enough maternal antibody present to interfere with vaccination, but not enough to protect from disease. Each animal responds at a different time. That time is specific for each animal and depends on amount and quality of first milk received, genetics, and the individual immune system. Active immunity is what we seek.
From an athletic perspective, the first time we meet the opposing team we don't know much about them (initial exposure) so it takes a while to gear up our defense. With a healthy team (strong immune system) and one game under our belt (previous exposure), we respond quickly and have the most likely chance of winning. (Assuming winning is important.)
Go for the series of vaccinations. Your four-legged companion is worth it.....
Mark W. Richards, MS, PhD, DVM