The first time I heard how vaccines worked I thought it was a miracle. With only a quick prick you could get immunity to something that otherwise could kill you. I was blown away. I wish it were as simple as it sounded in health class so many years ago.
In case it’s been a minute since you had health class, let’s have our own crash course on the principle behind vaccines. The immune system is capable of learning new “threats” in the form of bacteria, viruses, and others. When it identifies a virus as a threat it learns its unique identity and how to kill it. Once you fight a certain strain of a virus they say you’ll never get it again, but what they mean is that your body will recognize it and destroy it so quickly you’ll never again have symptoms.
Vaccines work on the premise of exposing the body to a disease, virus, or bacteria, but in a limited way that allows the body to identify this strain and form an immune response to it, so it can fight it later should the body encounter it.
When the body finds a new threat it will be better at identifying it and destroying it if it is similar to something it has dealt with before, such as a new strain of an old virus. A good example is the flu vaccination. The vaccine is developed each year from the current virus — for us in the United States they develop off of what’s in China the few months before our flu season. Since the virus is constantly mutating, the flu vaccine gives you exposure to the newest mutation, better preparing you for the mutation you are likely to experience if you are exposed to the flu virus.
The reason the flu vaccine needs to be developed every year is because the flu virus is rapidly changing. Rabies, however, does not rapidly mutate like this. It changes minimally, if at all, which is why the rabies shot is often only needed once in a lifetime — just remember, for liability reasons, most veterinarians recommend vaccinating against rabies at least every three years.
Why Doesn’t the Vaccine Infect the Body?
The reason you don’t get the disease when you are vaccinated is due to what happens on the manufacturer’s side. Some use a Modified Live Virus, which is a live virus that has been attenuated so that it can’t create the disease. The immune system will still see the organism as a threat and learn to destroy it.
Manufacturers can also make a vaccine using dead organisms. These cause no threat to the body they are administered to, but they may be less effective because the body recognizes they are dead and may not create as thorough a response to the disease. Manufacturers know this can lead to a lackluster response from the immune system, so many of these vaccinations have an adjuvant. An adjuvant is an immune-system stimulant that agitates the immune system for a greater response.
The adjuvant ingredient is where a lot of controversy on vaccines comes in. They are not always great ingredients to inject into living things. In children’s vaccines I’ve noticed many use aluminum. Not to get into a debate over the pros and cons of vaccines, but the decision you have to make for yourself is whether the risk of disease is worth it compared to dealing with a few toxins in your body. However, I will say that none of my adult dogs have ever gotten parvovirus and it is everywhere in the area I live. I trust the parvo vaccines.
**One caveat: there are some breeds of dogs who can be very susceptible to certain modified live viruses, so please do your research when vaccinating. As breeders, we need to know this stuff. In breeds, or genetic lines, where susceptibility to adverse reaction is likely, consider vaccinating with single-vaccines that only vaccinates for one thing, as opposed to combination vaccines like the 5-way or 9-way that vaccinate for multiple things. You can also reach out to your breed club to see how they recommend managing vaccinations.
In humans we get passive immunity from our mothers through the placenta and that immunity lasts in our system for about our first 6 months. The colostrum we receive from breast milk the first few days helps start the gastrointestinal tract off right, but its immune boosting power is minimal compared to what the placenta provides during pregnancy. This explains why breast-fed babies are generally healthier, but also why formula-feeding babies won’t inevitably be unhealthy. However, this whole process of getting our immunity primarily from the placenta prior to birth is unique to humans.
Dogs — like most mammals — work entirely differently. The colostrum a puppy receives in the first few days of life does EVERYTHING for his immune system. Colostrum is all his mother’s immunity crammed into a few ounces. After about three days the bitch no longer produces colostrum and the puppy’s intestinal tract will no longer be prime to receive immunity for colostrum, placing a short time window on the process. The milk she produces post-colostrum is designed to help the puppy grow. This is why during the first few days all puppies must be monitored to make sure they are getting their fair share of colostrum.
Passive immunity can be a little confusing, but to put it simply, it is immunity that the body can use but not create more of. Think of it as mom giving you a small army. Some of the soldiers specialize in fighting parvovirus, others in distemper, canine parainfluenza, etc.. This army consists of super great soldiers, but they have a short lifespan. They will die in a few weeks and no longer be able to protect the puppy. They are the puppy’s buffer while he builds up his own immune system.
With each passing week the strength of the passive immunity decreases until it becomes ineffective and eventually disappears. This loss of immunity over time is called diminishing immunity. While these immunities remain in the puppy, the puppy will not develop an immune response to vaccines, since the passive immunity — the soldiers gifted from mom through colostrum — will wipe out the vaccine before the pup’s immune system can be triggered. This is why vaccines do not work while passive immunity is present.
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The Susceptibility Period
As the puppies get older their mother-given, passive immunity starts to dwindle. Each immunity does this at a different rate and it even varies among puppies in the same litter. This means they may only be immune to Parvo through week six, but may be immune to distemper through week twelve. As these immunities diminish, inevitably they won’t be strong enough to protect the puppy from disease should exposure occur. However, they will still be strong enough to prevent a vaccine from triggering an immune response. Remember, vaccines are a weaker version of the disease by design, either due to them being dead or having been attenuated.
This fragile time — when mom’s immunities are insufficient and yet vaccines won’t take — is called the susceptibility period or window of susceptibility. It is the scary time when, despite whatever the owner/breeder does, the puppies are most likely to be infected if they come into contact with the disease.
Gauging the Susceptibility Period
Unfortunately there is no simple formula for determining the susceptibility period.
A dog’s immunities can be tested through titers, a test that assigns a number to a dog’s level of immunity to a certain disease.
Titers are a little sticky and can be confusing, so I’ll try and shed some light on how they work.
A titer measures the antibodies from an immune response. These can be from a vaccine or through actual contact with the disease. Showing a high titer amount tells us that the immune system has learned the disease and is able to build antibodies against it.
However, having lots of antibodies in the bloodstream is similar to wearing a lot of armor: you may have needed the armor while you were at war, but now you’re home, and you don’t really need to wear it to the grocery store.
However, since you already have the armor, there’s no sense getting rid of it when you could just hang it up in your closet should you need it later. This way you aren’t wearing out your system by wearing this heavy armor all the time.
Removing this armor is akin to the immune system reducing the number of antibodies floating around the bloodstream. The threat is no longer there, so the need to continually produce these antibodies declines. You still have the armor, you just put it in the closet, which is what an immune system does over time. It reduces the amount of antibodies in the bloodstream as they aren’t needed and waste energy for the animal, but it still stores the knowledge of HOW to make the antibodies. This information is stored in memory cells, and is much like storing the armor in the closet should it ever be needed.
This is why you could do a titer test years later and get a minimal result, indicating minimal immunity, but have the dog still respond well to the virus because the memory cells remember and the immune system can easily make the required antibodies. There is no way to test memory cells, so this is why titer testing isn’t always helpful, especially if it is done long after the vaccine or recovery from the disease.
There is a great article about titer testing — how to go about it, and when — by Dr. Laura Coger of the Healthy Dog Workshop.
The Vaccination Schedule
The reason we do a series of vaccines is because we are stabbing in the dark, hoping to give our dog the best opportunity to build immunity against some of the terrible diseases he could be exposed to. If we knew we could guarantee our puppies wouldn’t come in contact with any of these diseases until 16 weeks of age, then we would vaccinate at 16 weeks of age, once, and call it good. We just can’t guarantee that our yard hasn’t contracted parvo, so we try to vaccinate as early as it might work in an effort to give our dog the best chance possible.
We vaccinate again at a year to guarantee the vaccine takes and the immune system has developed antibodies. After one year of age, vaccination schedules become a source of discussion. The five main vaccines found in the 5-way puppy vaccine are distemper, parvovirus, 2 strains of adenovirus, and parainfluenza. There is a fair amount of research suggesting the immunity gained in this vaccine, administered either at 16 weeks or a year, is sufficient for lifetime immunity, as these strains do not mutate drastically enough to require further vaccination. The reason many are forced to revaccinate is due to legal ramifications, such as requiring annual vaccinations for dogs licensed in the city or for dogs who are boarded regularly at a kennel, where taking the chance of boarding an infected dog entails too much legal risk
Rabies vaccines are suggested at 12 or 16 weeks, while some veterinarians encourage waiting until as late as 22-24 weeks, although certain municipalities have a law regarding this. Most encourage a follow-up vaccination at a year, then generally every three years from there. Some suggest more frequently if there is a high probability of running into a rabid animal, but I have yet to find research suggesting rabies is a highly-mutating disease requiring a booster.
Many unnecessary vaccines are administered because people don’t know why they’re vaccinating or how immunity works, and are encouraged by others who are persuaded by fear or legal ramifications.
There are exceptions, though: bordetella and leptospirosis. These vaccines are actually less effective than others and create limited immunity that may diminish and fails to prevent infection, merely reducing symptoms. The jury is out as to why these vaccines don’t provide longer immunity. Some blame the manufacturer for wanting to sell more. But ultimately there is some evidence to suggest that vaccinating for things like kennel cough should be something you do only in certain circumstances, such as a location where contracting the disease is highly likely. It’s worth doing your own research to see if this is a good choice for you or your dogs.
Ultimately, I highly encourage vaccinating, but vaccinating with purpose and understanding — much the same as I encourage in EVERY aspect of your breeding program. I share this vaccination information because there seems to be a lot of confusion around it. I also worry that many feel if a dog was vaccinated at 8 weeks that he doesn’t need to be vaccinated again, but this really isn’t the case as we now know.
I encourage you to take the time to figure out the best vaccination protocol for your dogs and educate your buyers on the procedures that have worked for you.
I’ve created a pdf download with the standard vaccination protocol, and a few links to veterinarians challenging the standard protocols.
I’ve suffered through parvovirus before and I wouldn’t wish that on anyone. I know today’s episode wasn’t as exciting as some of the others, but I’m glad you stayed until the end. Understanding vaccines and immunity will not only make you more successful with your dogs and the health of your breeding program, but it will help you design your facilities and management to accommodate susceptibility windows.