By Lorraine Lopez-Soberal
Put yourself in this scenario… You take your 8-week old puppy to the veterinary hospital because she’s vomiting and has diarrhea. After some testing, the results come back as positive for parvovirus. Concerned, you look to the veterinarian and say “but doc, she had her first puppy shots two weeks ago. Why is she sick?”
Vaccines are complex formulations obtained from either inactivated or killed infectious organisms such as a virus or bacteria. Their purpose is to stimulate the immune system to produce its own antibodies against a disease. Vaccination results in immunity, or the ability of the body to recognize infection and either completely prevent infection or to simply reduce the clinical signs associated with a disease. But it is important to understand that no vaccine is 100% effective. In fact, the efficacy of a vaccine depends on multiple factors. The two most common factors that result in vaccine failure are the interaction between the puppy’s immune system with maternally derived antibodies (MDA) and improper handling and/or storage of the vaccine.
Among all the factors that may interfere with vaccine efficacy, MDA is considered the most common cause of vaccine failure. Puppies obtain MDA when they ingest colostrum, the first milk secretion from their mother, within the first 24 hours after birth. Colostrum ingestion is desirable because this milk is rich in antibodies that will provide neonates with protection against diseases that the mother has been exposed and/or vaccinated for. MDA interfere with vaccine recognition in puppies by “masking” vital areas in the vaccine molecule that are necessary for recognition by the immune system. This results in the inactivation of the vaccine. This interference can be overcome by starting vaccine series at the time when these antibodies start declining in puppies.
Maternal antibodies start decreasing around 6 weeks of age. This decline in protection can leave the puppy susceptible to diseases so it is very important to start vaccine series around this time. The first vaccine in a series is incapable of providing protection against disease, instead it prepares or “primes” the immune system to recognize the second vaccine so that it can start producing its own immunity. That is why it is of extreme importance to booster vaccines. Also, the 2nd vaccine in the series, which is given 3-4 weeks after the first vaccine will have a better opportunity to provide more protection because by this time MDA have further decreased. The third vaccine in the series is timed so that the puppy will receive it when he/she is around 12 to 16 weeks of age. It is then when MDA are at its lower levels and therefore should not interfere with vaccine efficacy.
Timing is crucial for vaccine efficacy. Usually protection provided by a vaccine is generated 8 days after the second vaccine. If a puppy is exposed to a disease before starting the vaccine series or in the interval between the first and 2nd vaccine, it is highly possible for it to become sick because the immune system has not had enough time to mount its own protection against the disease.
Proper handling of the vaccine is the second most common cause of vaccine failure. Vaccines are classified as either inactivated (killed) or modified live based on how the causative organism of the disease is prepared. Any exposure to heat, sunlight or chemicals either in syringes or the skin will result in inactivation of the vaccine. When you take your pet to a veterinarian, you can rest assured that the vaccine that your pet is receiving has had the proper handling and storage to ensure that none of these factors will result in a vaccine failure.
Vaccines are essential for providing protection against diseases. Vaccination series are scheduled so that they are administered at the time when maternal immunity is decreasing with the purpose of giving a boost to the puppy’s immune system. Even though no vaccine is perfect, the chances of a vaccine failure are low when they are administered at the correct time and have received the correct care before administration. Not only do vaccines provide protection against potentially deadly viruses that affect dogs such as Rabies and Parvovirus, but they also protect humans from getting diseases from their pets such as Distemper, Leptospirosis and Rabies.
Editor’s Note: at MSU-CVM, we recommend that a puppy not be taken into areas where it may be exposed to pathogens until completion of all vaccines. This may include dog parks and other areas where multiple dogs congregate.
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