Vaccines - Keeping Your Pet Protected
Published: December 28, 2012
By Michael R. Kelly, DVM, MS
Most of us who have pets are aware that they need to be vaccinated as part of their total health care but few understand why vaccines are so important and how they work. The issue is even more confusing when we see so many new types of vaccines and changing recommendations for vaccinating our animals. Getting more knowledge about how vaccines work and what is commonly recommended can help us make informed choices for our pets’ health.
What’s a vaccine? A vaccine works with the animal’s immune system to build antibodies against certain diseases. Most vaccines are designed to fight specific viruses, but there are a few that work against certain bacterial infections, such as kennel cough.
How des it work? The body has a series of complex mechanisms that work together like a security system to fight off microorganisms that could cause infections. This is called the immune system.
The first line of defense is the largest organ in the body- the skin. This large sheet of tissue acts as a physical barrier against the outside world. Openings into the body through the skin like the nose or mouth are lined with delicate mucus membranes that are designed to help trap “invaders” in sticky mucus and flush them out of the body. (This is why you have a runny nose when you get a cold- your nose is trying to flush out the cold virus).
The next defense is the lymphatic system which produces various types of lymphocytes, or White Blood Cells. The sole reason for WBCs is to attack any invader and ward off infections. White blood cells often die while fighting infection- pus is composed of dead wbcs. Some WBCs act like security guards and stay in tissues like the mucus membranes to wait for and kill any foreign cells that pass by. Most of these devour the invader or kill it with chemicals.
Others are like security patrols circulating throughout the bloodstream and even squeezing between cells to seek out and destroy any antigens they contact. The most specific and deadly of these are the antibodies. These are engineered by the body to seek out and destroy a specific infectious agent.
How does the body know what is an invader and what is normal tissue? The immune system can identify every cell by a certain protein “tag” called an antigen. Every cell in your body has a tag that says it belong to you. When a piece of protein or a cell gets into the body and doesn’t have that “you” tag, chemical alarms go off to alert the immune system. The amount of response depends on what kind of foreign protein it is or how much foreign material is present.
This is why transplant patients must take immune suppressing drugs to keep their bodies from rejecting the organ. The body doesn’t know that the organ is good for it, it only knows that the organ doesn’t belong to the patient so the cells attack it. This is also why people and animals are allergic to proteins and not to things like rocks. Oh yes, an allergic reaction is when the immune system overreacts to an antigen.
There are even diseases where the body’s immune system turns against itself. These are called autoimmune diseases like rheumatoid arthritis or Lupus.
Why do Vaccines Work? We introduce antigens of the actual disease into the patient and allow the body time to engineer specific antibodies aginst it. The goal is to challenge the immune system enough to get it to make the antibodies while making sure we don’t cause a real infection.
One way to do this is to take the virus and inactivate it with a chemical. The actual virus is dead but the antigenic protein tag is intact to stimulate the wbcs to produce antibodies.
Modified Live Vaccines contain actual live virus that have been changed genetically just enough to not cause disease but the immune system still can recognize it and create antibodies. The latest technique uses genetic engineering to break the virus apart and utilize only the appropriate antigenic fragment.
In a healthy patient, the body is able to create enough antibodies in about 14 days to protect against the disease. If the patient is already sick with the virus, giving a vaccination won’t help because it would take too long. It’s sort of like closing the barn door after the horse has gone.
How are vaccines administered? Vaccines used to be given by the subcutaneous (under the skin) or intramuscular (into the muscle) route only, but recent advances have made available other routes that could be safer and make for better responses in some cases.
For instance, the vaccine for bordetella (kennel cough) can be given subcutaneously but the preferred route is directly into the nostrils (intranasal) where it can get the best effect and allows for less injections.
Research into the possible link between injectable vaccines and some tumors have resulted in the development of needless injection systems and more intranasal vaccines, especially for cats, a species tha has a rare but deadly cancer linked to certain injectables.
Why does mypuppy or kitten need so many boosters? The immune system of all babies takes time to grow and develop sufficient immunity on its own. In the meantime, immunity in the form of actual wbcs from the mother is transferred to the baby while in the uterus and when it drinks the colostrum at the first nursing. This is called passive immunity and usually lasts for less than 12 weeks.
The goal is to stimulate the baby’s antibody production to establish active immunity before the mother’s passive immunity wears off. There is no way to predict when passive immunity wears off and active immunity starts, so your veterinarian will administer a series of injections timed every 3-4 weeks until at least 16 weeks of age.
IMPORTANT NOTES: All puppies and kittens are considered undervaccinated and susceptible to those diseases until they have completed the series of vaccines. Do not take your puppy to the park to visit if he’s only had 1 or 2 injections- he could still get the deadly parvovirus infection.
Very rarely, some animals may become ill with the viral infection even after getting all the right vaccines because of some malfunction of their immune response.
Some animals may have an allergic response to a vaccine. Signs of allergic reactions are often itching, hives, swelling or vomiting. If your pet has any of these signs or you are worried about any changes in your pet after a vaccination, call your veterinarian immediately- this can be a serious condition which needs immediate medical attention.
My pet had all his vaccines as a baby- Why do I need yearly boosters? Depending on the disease and the pet’s immune system, the antibodies may decrease over time.
Administering a booster encourages the system to keep immunity optimal.
Recent advances in vaccine research has resulted in the development of vaccines that can last longer than a year.
Many veterinarians are opting to design vaccination plans for each pet based on inividual needs and to space vaccines out over several years.
For example, your veterinarian may elect to give your adult dog a Distemper vaccine and a Rabies at 1 visit then give a Parvovirus booster the next year, then administer another Distemper and Rabies on the 3rd year. This type of plan lowers the risks associated with vaccinating while providing adequate immune response to prevent disease.
To make sure your pet gets the best protection, follow your veterinarian’s plan for vaccinations.