by Dr. Bernstein
LOS ANGELES, CA – Can you imagine a world without vaccines? A world with diphtheria, typhoid, poliomyelitis, smallpox and rabies running rampant through the population? Fortunately, prevention against many serious diseases is readily available. Our animal population is likewise protected against many serious diseases by vaccination.
Most pet owners know their dogs and cats should be vaccinated, but there is often confusion as to when or why. Veterinarians are sometime presented with a very ill puppy because the owner was told (usually by a well-meaning friend) that vaccines should be started at a later age. Another common scenario is an animal that was purchased with the understanding that it “had all of its shots”, yet develops canine parvovirus enteritis or feline distemper.
It may be helpful to understand why these illnesses occurred. The answer lies in understanding “maternally derived antibodies”. Antibodies are produced by the immune system of the pregnant mother in response to exposure to a vaccine or a disease-causing organism. These protective antibodies are passed on to the newborn when they nurse colostrums (first milk) during the first few days of life. These antibodies protect the baby from disease for a limited period of time. If the youngster is vaccinated while it has high levels of maternal antibodies, the antibodies will attack the vaccine virus. The antibodies cannot distinguish between a vaccine virus (good) and a pathogen (disease-causing virus). For this reason, the puppy/kitten needs to receive a series of vaccinations until the maternally-derived antibody level has decreased sufficiently to prevent its cancellation of the vaccine virus. We know that this will occur by 16 weeks of age, so that is the age at which we are virtually certain that the vaccine will be effective. The youngster will therefore make his own antibodies against the disease.
One might think that waiting until the puppy/kitten is 16 weeks old would be a way to avoid maternal antibody interference (remember the well-meaning advice to wait until the new pet was older?). In theory, this is true, but if the antibodies decrease prior to this age, the young one will be susceptible to infection. The vaccine series is the attempt to make the window of susceptibility as small as possible.
Your veterinarian will explain his or her vaccination program at your first visit. The ideal age for the first visit is at 6-8 weeks. We all want your new family member to start off with at least an “ounce of prevention”.