We tend to fear the things that we don't know; death, aliens, our new neighbors - it's almost a rite of passage as human beings. We struggle to come to grips with confusing topics that push our minds to the limits of our understanding, in attempt to soothe our concerns. As pet owners, one of those topics that can often push our understanding is vaccinations. We know our animals need them (our vets tell us that), but with so much information out there from other sources, it can be easy to find information that contradicts what our vets tell us. We don't mean to doubt the professionals, but we just want what's best for our four legged (and sometimes other legged) best friends.
The fact of the matter is that at their core, vaccines are incredibly well designed. The intent behind them is simple; give your immune system a taste of what foreign bodies look like, so that if we're exposed to them at a later date, there's no shuffling around, trying to figure out what they are.
Every animal is born with an immune system that is effectively useless. It's never been exposed to any pathogens (that's part of the safety of developing in a womb for however long they gestate), so the immune system has no way of knowing what anything looks like, outside of the cells that make up the body to begin with. Until an animal is 6 weeks old, the immune system is immature and useless, which is why it's often recommended that puppies and kittens be kept away from other animals until they've had time to develop. It's also why animals are recommended to be left with mom.
Initially, these newly born creatures have what are called maternally derived antibodies; antibodies that their mom has produced and given to them via colostrum (a main reason why it's always recommended that newborns be encouraged to feed as soon as possible). For the first 6 weeks of an animal's life, these antibodies don't register as foreign, despite not having markers that help the body know what is "self" and what is "not self." For this short period, the immune system is learning to walk; stretching its legs and starting to explore, probing the body for foreign particles to examine, digest and develop a set of stored information that will allow a stronger response in the future.
Between 6-12 weeks of age, the immune system of an immature dog or cat is going through massive amounts of changes. All the antibodies that they've gotten from their mom through milk are suddenly being recognized as foreign. The immune system is now strong and smart enough to be able to sort through these antibodies and develop concern, since they don't belong. At the same time, it's also busy making antibodies of its own as the animal is exposed to more and more of the world. We try to keep environments clean for newborns and young animals (and humans), but complete sterilization is impossible and actually prevents them from developing the much needed antibodies.
After 12 weeks, the immune system is up and running. It knows its job and is ready to defend the body, should any outside invasion occur. Up until then, the internal battle between mom's antibodies and baby's antibodies, may interfere with the effect of the vaccination. It's why multiple doses of vaccines are required, because we can't be absolutely positive that we've achieved the right levels.
Since the immune system is in early stages, giving multiple doses (boosters), may seem unfair, but it's absolutely necessary. The level of antibodies in the blood needs to reach an appropriate level, or the protection of the animal is not fully achieved and the vaccination may not be effective. By the time that an animal has had a full set of boosters, the immune system is likely to have reached this level. If we test these levels, we look to see how many dilutions of a blood sample can be made, while still being able to detect antibodies. Ideally, you want to be able to dilute A LOT.
Boosters are given annually or every three years (or some variant, depending on the vaccine). This is to ensure that the antibody levels in the body remain at competent levels, as there is a natural downward trend as animals get older. The immune system will decay in the same way that the rest of the cells do and so to ensure successful vaccinations, boosters are given. Contrary to what may be suggested, these boosters are NOT a means to get more money from clients, but a means to ensure that patients are continually protected from communicable diseases through their life.
The other thing that can be scary about vaccines is simply considering what's in them. I mean, your vet wants to inject your animal with a vaccine that contains a virus that could kill it!? Not quite.
Vaccines are one of four types; toxoid, whole organism, subunit antigen or recombinant DNA. The first two are more common and widely used, while the latter are more current and on the cutting edge, but less widely used - right now.
Toxoid vaccines are against things like Tetanus - a disease caused NOT by a virus or bacteria, but by a toxin that is produced by the bacteria. In a laboratory, the toxins are isolated and modified to remove the toxic component, while leaving in the markers that the immune system uses to learn that this particular toxin is foreign. This allows the body to identify Tetanus toxins and destroy them, before the harmful effects of the toxins are able to result in the paralysis.
Whole organism vaccines are either killed virus or modified live viruses. As one would guess, a killed virus is one that has been killed by either chemicals or radiation, leaving the cells intact so that they can be injected. With no means to replicate, they cannot replicate and cause disruption to the body, but their presence acts as a template to allow the body to learn what not to invite in. Modified live viruses sound terrifying (I mean, they ARE alive) but that's not the case. Modified viruses are cultured in a laboratory in unique and unusual conditions, driving natural selection until the only viral particles that can survive, are the mutant versions. These versions have selected for such an unusual environment, that when they're injected into an animal with standard conditions, they simply cannot thrive. The body can use them to learn, before killing them off. (Parainfluenza in cattle is cultured at lower temperatures, developing a version that will only replicate in cooler temperatures. Since the lungs of a cow are warmer than those of the nose, the virus is only able to replicate in the nose, resulting in a runny nose and cold symptoms, rather than development of pneumonia).
In the simplest of terms, recombinant virus vaccines are grown in a lab, at which point the proteins produced by viral cells, are taken away, since this is the part the body recognizes. These proteins are then introduced into the plasmid of a bacteria or virus that cannot replicate in the animal in question. For instance, one form of Feline Leukemia vaccine is carried by canarypox - a disease that CANNOT complete a lifecycle in a cat, because ... well, because a cat is not a bird.
At the end of the day, every vaccine is thoroughly tested and examined before going onto the open market. They aren't about making money and they aren't about dragging you into the vet once a year; they've been developed to provide your animals with a means to extend their lives and prevent unnecessary deaths from diseases that can be prevented. Without up to date boosters, there's no guarantee that, despite having been previously vaccinated, that your animal will still have the necessary antibody levels to combat a virus if encountered. Do you wanna take that risk?
Zoe is a second year veterinary student, studying at the #3 globally ranked program at the Royal Veterinary College in London. When she isn't studying abroad or logging hours with veterinarians, she's a Kennel Supervisor at Club K9, where she brings her wealth of knowledge and medical background to the staff team. Her own dog (a miniature aussie named Rue) is a regular and much loved member of the Club K9 pack.