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The Great Dog Vaccination Debate

Vaccinating our dogs is no longer a one-size-fits-all but every dog should be vaccinated. This much is simple.

Vaccination of dogs (and cats) protects them from infections that may be deadly or cause serious disease. However, the way we go about vaccinating our pets has changed over the years. Not so long ago, it was common practice to vaccinate every dog every year with a combination of vaccines

Here in Australia, the usual choice was called a C5, which includes parvovirus, distemper, infectious canine hepatitis, canine parainfluenza virus and bordetella bronchiseptica.

This was considered medically appropriate and a good choice from a legal standpoint because this is how the products were licensed to be used.

It is no longer deemed necessary to give dogs a C5 every year, and we should not be giving our pets any more vaccinations than they need.  

There are some vaccines, such as those for “kennel cough” that still need to be given every 12 months to be effective, and every dog should still go for their annual health check.

Expert groups have been convened to offer guidance on the best way to vaccinate our pets. 
The main group that many of you will have heard of is the World Small Animal Veterinary Association (WSAVA) Vaccination Guidelines Group (VGG)These experts in small animal microbiology, immunology and vaccinology have put together guidelines based on current scientific knowledge.  

These guidelines are the resources to consult when researching vaccination of our pets – NOT certain internet individuals and groups who lack scientific credibility and promote misinformation that often suits their own agenda. Poor advice and fear-mongering from these latter sources has been responsible for some well-meaning pet owners refusing vaccines when offered by their vet. Please, do your research – but use reputable, scientific sources, not those touting the latest all-natural fad. 

Dr Michael Day is chairman of the WSAVA Vaccinations Guideline Group. His research focus is on companion animal immune-mediated and infectious diseases, and he has published over 325 papers in the field of immunopathology as well as authored several veterinary textbooks. You would be hard pressed to find a more highly respected or qualified expert on the subject of vaccination.  

His words are simple – “Failure to appropriately vaccinate your dog or cat makes them susceptible to lethal infectious diseases, and the benefit of vaccination far outweighs any risk of an adverse event following vaccination.” For many, those words are enough. For those wanting a little more information and a deeper understanding, read on.
I encourage every pet owner to have an interest in their dog’s health and well-being and to always ask questions.

How Does Vaccination Work?

A basic understanding of the immune system can help to understand why we vaccinate our pets (and ourselves).  There are two basic halves to the immune system –these are called innate and adaptive immunity.

The Immune System – in a Nutshell

The innate immune system is the first line of defence and reacts quickly but non-specifically to threats. Most vaccines do not stimulate this part of the immune system.

The adaptive immune system takes a little longer to work but is more powerful than the innate immune system and has two very important qualities. 

Firstly, it can specifically target the particular infectious agent that activated it.  Secondly, it can remember infections that it has seen before.  The main players in the adaptive immune system are the lymphocytes and antibodies. B lymphocytes make antibodies while T lymphocytes have other jobs including a process called cell-mediated immunity that does not involve antibodies.  In many infections there is a role for both antibody and cell-mediated immunity in the protective immune response. 

At the conclusion of any immune response, some long-lived lymphocytes retain the memory of that infection, so that future infections are met with a rapid and effective response.  This is the basis of how vaccination works.  When we give a vaccine we are administering a harmless form of an infectious agent leading to generation of an adaptive immune response and creating memory.

Where it starts to get a little complicated ...

The effectiveness of the immune system of any individual dog is partly determined by their genetics.  This is most obvious when we see breed-dependent differences in responses to vaccinations, for example some populations of Rottweilers are unable to make protective immune responses to parvovirus infection (or vaccination).  This, and something called maternally-derived antibody (MDA), is part of why one size does not fit all.
Mum’s immunity protects her babies but also blocks vaccines. Newborn puppies take in antibodies when then drink the colostrum (first milk) from their mother.  These maternal antibodies are absorbed during the first day of life and protect the puppy during their first weeks while their own immune system is developing. MDA is essential for survival during those early weeks. 

However, its presence also prevents the puppy from making its own immune response – and also from responding to vaccines.  Knowing exactly when a vaccine will be effective in any given puppy is difficult.  

The runt of the litter that received less colostrum might be capable of responding to vaccination at 8 weeks of age, whilst a bigger pup from the same litter who got more colostrum may still have persisting MDA blocking their own immunity until 12 weeks. This is why we recommend the last dose of core vaccines for pups be given at 16 weeks of age or older

Unfortunately it’s not feasible to test dams for antibody levels or measure the level of MDA in an individual pup, so repeated vaccination is given – usually around 8, 12 and 16 weeks of age.  
Why not wait until 16 weeks to vaccinate them all and just do it once? 

Because the puppy whose MDA is gone by 8 weeks will be totally unprotected from deadly diseases for 8 weeks.  In particular this is the age where they are at a very high risk of parvovirus

It would be possible if the pups were kept in complete isolation until they were actively immunised, but this is impractical and inadvisable. A puppy who receives no socialisation prior to 16 weeks of age is likely to have a lifetime of problems.

There will still be occasional dogs who are unable to respond by the 16 week vaccination and for this reason we must do one more, usually at either 6 or 12 months of age, to catch these guys and ensure they are covered. 

An alternative to this last vaccination is performing a titre test to check if they are adequately immunised, which is discussed below.

There are a few animals that will be non-responders – that is, they just can’t develop antibody to the virus, regardless of how often they are vaccinated. It is estimated that the number of non-responders to parvovirus is 1 per 1,000 dogs and to Distemper is 1 per 5,000 dogs in the general population.  The non-responders, if infected, will often die.

When the population level of immunity (the ‘herd immunity’) falls below about 65%, there is a risk of outbreaks of that infectious disease. Vaccinating your pet therefore not only protects him or her from infection but is to the benefit of the entire dog population, including those non-responders who are most at risk.  

What are we protecting our dogs against?

Core Vaccines

The core vaccine for Australian dogs is called C3. It covers canine distemper, canine infectious hepatitis and canine parvovirus.

1. Distemper

Canine Distemper is a highly contagious and often fatal disease of dogs throughout the world.  It is still seen commonly in developing countries and also in western countries where animals have not been vaccinated due to negligence or owner beliefs. Eradication of this disease isn’t possible because the virus occurs in wild animals that can then reinfect domestic dog populations.

Distemper can cause respiratory disease with severe pneumonia, gastrointestinal disease, neurological disease, and severe suppression of the immune system leading to infection by normally harmless bacteria and viruses. Common signs are a yellow discharge from the nose, vomiting and diarrhoea, excessive drooling, coughing, laboured breathing, crusty discharge from the eyes, loss of appetite and weight loss. There can also be muscle twitching and seizures.

Vaccination provides prolonged immunity in about 99% dogs receiving a single dose of modified-live vaccine at or after 16 weeks of age.  Dogs develop protective immunity within a few days of vaccination. Distemper is a vaccine preventable disease.

2. Infectious Canine Hepatitis

Infectious canine hepatitis is caused by canine adenovirus type 1 (CAV-1). Thankfully the disease has been recognized rarely in the last decades in those countries with effective vaccination programmes.

It is still prevalent in developing countries where only a small percentage of dogs is vaccinated and in wild animal populations worldwide.  This means vaccination must be continued in order to prevent outbreaks of this devastating disease. Around 20% of infected animals will die, and this is closer to 50% in dogs less than 12 months old.

Signs are most commonly due to hepatitis and can include lethargy, fever, vomiting, diarrhoea and discharges from the nose and eyes.

Dogs are vaccinated for infectious canine hepatitis using a modified-live CAV-2 vaccine which provides cross-protection for CAV-1 and is safer than using CAV-1 itself.
Infectious canine hepatitis is a vaccine preventable disease.

3. Canine Parvovirus

Canine parvovirus is a common, deadly infectious disease of domestic and wild dogs of all ages. Puppies under six months of age are the most severely affected, and most will die without intensive and very costly treatment. 

Porthos (9 months) and as a
puppy first diagnosed with Parvovirus
Adult dogs will not necessarily develop disease when infected, but they will shed virus in their faeces and potentially infect susceptible puppies who can then die. 

Parvo is not only spread directly from dog to dog but easily on contaminated shoes, clothing and other materials. It can survive in the environment (cages, kennels, grass, soil) for a year.

Signs of infection include inappetence, depression, fever, vomiting and diarrhoea, which is often bloody.  Death can occur within one to three days. Parvovirus can be killed with appropriate disinfectant, but this is not effective in some areas such as grass and soil.  

It is critical that new dogs introduced into an area where parvovirus has been, are vaccinated and have developed protective antibody. If they are not protected by vaccination, they are likely to get infected and die. 

The parvovirus (CPV-2) vaccines, regardless of what variant they contain, stimulate an active immune response that provides long term protection from all current CPV-2 variants (2a, 2b, and 2c). Parvovirus is a vaccine preventable disease.

4. Non-core Vaccines

So we know that our C3 (Distemper, Parvo, Hepatitis) are our core vaccines and are non-negotiable.  What about other vaccines?  

The main ones we consider in Australia are parainfluenza and bordetella, together often referred to as “kennel cough”.  These vaccines induce only short-lived immunity or may simply reduce the clinical signs of disease rather than preventing actual infections.  Because they are less effective, they need be given more frequently in adult animals (as ‘booster vaccines’) in order to retain the immune response. We recommend vaccinating for parainfluenza and bordetella every 12 months in dogs at risk of these infections.

Current international guidelines for vaccination of dogs

Guidelines for canine vaccination began development due to the growing awareness that many vaccines provided a long duration of immunity and therefore did not need to be administered yearly. Like any medical treatment, adverse reactions do occasionally occur following vaccination of dogs, and so unnecessary vaccination should be avoided. 

VGG recommendations may occasionally differ from those made by the manufacturers of vaccines (manufacturer’s recommendations for specific products are supported by studies conducted to obtain a license to sell that product). 

Your veterinarian might decide to follow the advice given in guidelines, even if this conflicts with manufacturer’s recommendations, but should ask for your consent to do this.
The current recommendation is to start vaccination at 6–8 weeks and to revaccinate every 2–4 weeks with the last dose at 16 weeks of age or older.

Following the initial puppy course the VGG recommends revaccination at either 6 months or 1 year of age, then not more often than every 3 years.  If titre testing (see below) is elected instead of the first booster, it can be performed from 20 weeks of age in a puppy that received a vaccine at 16 weeks.  
Puppies with positive results will not need to be vaccinated (or retested) for another three years.  

There are some breeders that recommend their pups not be vaccinated with certain vaccines. If those vaccines are non-core (optional), those recommendations may be acceptable. However, if they are core vaccines, not vaccinating is unacceptable. There should be no dog that does not receive the three core vaccines.  There are also some breeders that recommend splitting doses of vaccine between small puppies. The dose of vaccine is not related to the size of the dog and doing this may result in vaccine failure.  Every dog needs a complete dose.

Titre Testing – another option

Rather than automatically revaccinating adult dogs every three years for the core diseases, another option is called titre testing.  A simple blood test can determine whether an individual adult dog already has immunological protection against these three diseases. If they do, revaccination is unnecessary.

In Australia, titres can be run for all three of our core diseases – Distemper, Parvovirus, and Hepatitis. We don’t run titres for canine cough because it’s not useful. The duration of immunity for canine cough pathogens is 12 months at best, and we must vaccinate annually for those who need it.
Titre tests can be run in the veterinary clinic using kits that your veterinarian can purchase, or alternatively the blood sample can be sent to an external lab for testing. External lab tests cost more and take longer but are more accurate. In-clinic testing is likely to be adequate in most circumstances.  Currently the cost is generally more than a vaccine but no longer significantly so.

Titre testing is great, but it has limitations that we need to understand.  There are so many variables to the immunity produced by vaccination.  The vaccines themselves are not all the same. The individual response of each dog to a given vaccine can also vary widely, depending on their previous exposures to the pathogen, presence of other illness, age etc.  

All of these factors mean the duration of immunity given by a single injection will not be the same from dog to dog.  So what does a positive titre mean? Sure, the dog is protected on the day that blood sample is taken, but for how long?  To date there are no international guidelines to suggest how long we can expect a high titre to stay high for the average dog.  Current advice is that testing should performed every 3 years, but in dogs older than 10 years, this should be done annually

Adverse effects

Despite being incredibly safe, there can never be a guarantee, in either human or veterinary medicine, that every single administration of a vaccine will be perfectly safe and without adverse consequences. 
On rare occasions, vaccination of a dog or cat might lead to an unexpected clinical reaction. Such reactions are for the most part mild and inconsequential and a simple risk benefit analysis will always suggest that the benefit obtained from having solid immunity to potentially lethal disease far outweighs the small risk of a vaccine-associated adverse event. 

A recent paper based on data compiled from millions of North American veterinary records examined reactions occurring within 3 days of vaccination in 1.2 million dogs receiving 3.4 million doses of vaccine. The prevalence of any type of documented reaction was 38 dogs per 10,000 vaccinated - but the majority of these reactions were mild and of no consequence.

Some adverse vaccine reactions are not observed until days, weeks or even months and years after vaccination or revaccination. Injection site sarcomas in cats may not develop for years after being triggered by vaccines or other injections.  

Some people say vaccines cause autoimmune disease, but there is no scientific evidence that this is so. From the WSAVA vaccination guidelines:  “Vaccines themselves do not cause autoimmune disease, but in genetically predisposed animals they may trigger autoimmune responses followed by disease – as can any infection, drug, or a variety of other environmental factors.”  

Unfortunately, at times vaccines and vaccinations are often mistakenly blamed for causing or triggering various diseases and disorders when the vaccines are not responsible, and other factors (e.g. drugs, environmental contaminants, toxins, chemicals, infection or purely hereditary factors) are the cause of the problem. Often it is difficult or impossible to know if the vaccines and not something else caused the problem, because there are often multiple causes. As stated previously, UNDER NO CIRCUMSTANCES should any breeder or owner NOT vaccinate their animal at least once at 16 weeks or older with the core vaccines because they are concerned about adverse reactions.

So which vaccines does my dog need and when?

Simply not vaccinating is not an option. The risks of contracting life-threatening infectious disease remains potentially high, even in developed countries. Your veterinarian should discuss core versus non-core products, frequency of administration and the option of titre testing with you. Together you can work out what’s best for your individual dog.

written by Dr. Joanna Paul, May 2018 for Australian Dog Lover (all rights reserved).

About the writer:

Dr Joanna Paul is a Melbourne-based veterinarian who has been working in partnership with pet parents to care for their furry kids for over a decade.

As well as work, she divides her time between her gorgeous dog Billy, a menagerie of other fur kids, three children and her own blog for pet parents.

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