Preventing Unnecessary Over-Vaccination in Dogs and Cats

Is Your Dog or Cat Over-Vaccinated?

Rational Dog and Cat Vaccination Schedules

What does over-vaccination even mean? Surprisingly, I’m not talking about the number of vaccines given during one visit. Because sometimes your pet really needs all of the vaccines! It is not ideal to administer too many vaccines in one visit. Nobody likes that many jabs. However, that doesn’t count as over-vaccination. Over-vaccination occurs in 2 situations: your pet receives unnecessary vaccines, or your pet receives necessary vaccines too often. Unfortunately, many veterinarians don’t understand the duration of immunity (DOI) or risk-benefit analysis. Don’t let your vet over-vaccinate your pet due to your lack of education on the matter.


  1. Risks of Over-Vaccination
  2. Core Dog Vaccines
    1. Canine Distemper Virus
    2. Canine Parvovirus
    3. Canine Infectious Hepatitis
    4. Rabies
  3. Scary Video about Rabies
  4. Non-Core Vaccines in Dogs
    1. Leptospirosis
    2. Kennel Cough
    3. Lyme Disease
    4. Rattlesnake
  5. Core Cat Vaccines
    1. Feline Viral Rhinotracheitis
    2. Calicivirus
    3. Panleukopenia
    4. Rabies
  6. Non-Core Vaccines in Cats
    1. Feline Leukemia
    2. Chlamydophila felis
    3. Feline Bordetella bronchiseptica
  7. Vaccine-Associated Sarcoma in Cats
  8. Core Vaccine Administration
  9. Over-Vaccination by Too Frequent Vaccination Administration
  10. Over-Vaccination by Unnecessary Vaccination
  11. Rational Vaccination Schedules
  12. Conclusions

Risks of Over-Vaccination

What’s the big deal about over-vaccinating a dog or cat anyway? Glad you asked.

  • Increases the risk of vaccine-associate malaise. Malaise is a natural result of vaccination; it means the immune system is kicking it into high gear and doing all the things it should do to protect your pet from disease. But getting a lot of vaccines at once means that your pet could feel pretty bad for a couple of days. I’m always happy preventing my pets from feeling bad, so I don’t like to give them any more vaccines than they need at any particular time.
  • Increases the risk for Vaccine-Associated Sarcoma in cats.
While this was a copperhead bite, a vaccine reaction looks exactly the same
  • Increases the risk for vaccine reactions. Back when Banfield was the King of Over-Vaccination, they documented that the number of jabs given in a single visit significantly increased the risk of potentially serious vaccine reactions, especially in small dogs. As a result, they do not administer as many vaccines in one visit as they used to. Give them credit for keeping track of such things!
  • Increases the risk for anaphylaxis. The immune system has to be sensitized to multiple exposures to any antigen, including vaccination, to cause a severe reaction. The more times you expose an individual to a particular antigen, the more you sensitize the immune system. Increasing the frequency of vaccination increases the risk for sensitization and therefore anaphylactic reaction.
  • Wastes money. I’d rather your pet health care dollars be spent on things that actually benefit your pet. $30 for a vaccine is another couple of months’ worth of heartworm, flea, tick, and intestinal parasite prevention.
  • Provides a false sense of security. Administering a 9-way vaccine to a dog who only needs a DAP doesn’t protect the dog from any real risk.
  • Most important IMHO: lying to pet parents about the duration of immunity of vaccines causes serious harm to my profession and erodes public trust. That is absolutely unacceptable to me.

Core Vaccines

Core vaccines protect a dog or cat against a common, dreadful, and possibly fatal disease. We designate them “core” because we deem every dog or cat susceptible and therefore we vaccinate them all. Rabies is a core vaccine in both dogs and cats.

Core Dog Vaccines

Besides rabies, the core vaccines in dogs are distemper, parvo, and adenovirus-2. A brief description of each disease follows.

Canine Parvovirus

In Family Veterinary Mobile Clinic’s service area of Sanford NC, we consider parvovirus to be endemic. This means that parvovirus is so widespread, that it is impossible to avoid. Unvaccinated dogs of all ages, especially puppies, are at extremely high risk for disease.

Treating parvo usually involves expensive hospitalization for IV fluids. Photo courtesy of Cornell College of Vet Med.

I’ve worked in this area for a long time. In my tenure at Animal Hospital of Fayetteville and at Small Animal Emergency Services in Vass, I’ve treated hundreds of puppies for parvovirus. We have extremely safe and effective vaccines to protect puppies against parvovirus. So it makes me very sad to think about all the furbabies that died, the families who were heartbroken typically due to ignorance, and the suffering of the puppies.

Let me be clear: vaccines when properly administered save lives.

Parvovirus in dogs causes several problems:
  • It destroys the inner lining of the GI tract, causing that tissue to slough out along with painful severe bloody vomiting and diarrhea.
  • Because of frequent diarrhea and vomiting, these puppies get severely dehydrated very quickly. They can’t hold down water, even if they wanted to drink or were given water by mouth. Only IV fluids can help.
  • Parvovirus also attacks the bone marrow where white blood cells are made. White blood cells are the body’s first defense against infection. Without white blood cells, puppies with parvo often become septic (widespread infection). If the dehydration doesn’t kill them, sepsis often does. This is why we give antibiotics during parvo treatment. The antibiotics don’t kill parvovirus; nothing does. We’re only treating or preventing secondary bacterial infections.
  • In very young puppies, it can also cause heart failure by directly destroying the heart muscle. There is nothing we can do about this.

Canine Distemper Virus

We’re lucky in this area that canine distemper is not that common- yet. I expect that distemper will be more common in this area in the future due to people moving and the constant movement of rescue dogs. However, distemper doesn’t last long in the outside world as parvo does. Without direct exposure to an infected animal, it is unlikely for a puppy to contract distemper. Canine distemper affects many species including most canine species (wild dogs, foxes, wolves), mustelids (ferrets, skunks, minks, wolverines, martens, badgers, otters), most bears, raccoons, and large cats. Feral dogs are the reservoir for infection and genetic shift causes canine distemper to infect other species.

Distemper causes several serious problems in dogs:

  • First, puppies get respiratory disease in the form of very thick discharge from their eyes and nose. They also usually have a fever and decreased appetite. They can develop coughing and severe pneumonia.
  • Next, the vomiting and diarrhea start. While typically not as severe or bloody as with parvovirus, the poor puppy is already suffering from respiratory symptoms too. They’re usually REALLY sick at this point and need intensive care in a 24-hour hospital.
  • If they survive, the virus then attacks the central nervous system causing seizures that may last for the dog’s entire life. Some never regain normal neurologic function.

Surviving puppies often have stained and pitted adult permanent teeth due to distemper infection as well.

Here’s the weird thing about canine distemper: some dogs get severely sick and die, and others hardly bat an eye. We have no way to predict which puppies will be severely affected and which ones will bounce back quickly. We have no idea which ones will develop severe neurological signs and which won’t. There is no reason to risk distemper infection in your puppy.

Canine Infectious Hepatitis

Canine Adenovirus-1 causes canine infectious hepatitis, a severe disease of the liver. We very rarely see this disease anymore except in bad breeding situations because the vaccines are so effective, and it doesn’t last very long in the environment. There used to be a vaccine for canine adenovirus-1 but it caused a lot of reactions, the most memorable being “blue eye” due to corneal edema.

Corneal edema due to CAV-1 infection (or vaccination). Photo courtesy PubMed.

As it turns out, the modified live injectable vaccine for canine adenovirus-2 is cross-protective against canine adenovirus-1 and doesn’t have those untoward side effects. Unfortunately, the intranasal canine adenovirus-2 vaccine, which is for kennel cough, does not cross-protect against canine infectious hepatitis. So we do use an injectable canine adenovirus-2 vaccine for our puppy series.

Rabies in Dogs

Rabies is a 100% fatal disease in dogs and with few exceptions, also humans. To date, 29 people in the entire course of human history have survived rabies, and 19 of them had moderate to severe permanent neurological conditions. Those are terrible odds, my friends. Every year, over 50,000 people die from rabies, and 99% of them get rabies from dogs. The vast majority of these deaths occur where rabies vaccination of dogs is lacking, namely India, which accounts for 35% of the total number of human rabies deaths in the world.

Several countries, including the USA, Canada, Japan, Western Europe, and some Latin American countries, have eliminated dog-mediated rabies solely because of government-mandated vaccination of dogs. Without rabies vaccine requirements, we could end up just like India, where over 20,000 people die every year from rabid dogs.

The US reports 60-70 rabid dogs every year, despite widespread vaccine requirements. The reason this is so dangerous is that we live with dogs. A rabid dog has the potential to infect a lot of people. 6 dogs tested positive for rabies in North Carolina in 2020, the last year we have statistics.

Scary Video about Rabies

May be disturbing to some viewers!

Because we don’t see rabies that often, we tend to underestimate its importance. The only reason we don’t see rabies is because of the government-mandated vaccine requirements in dogs (mainly) and cats. If you are bitten by a mammal of unknown rabies vaccine status, and that animal can not be tested for rabies, seek medical attention immediately. Post-Exposure Prophylaxis (PEP) is almost 100% effective in preventing rabies in humans. Once you start to have clinical signs, treatment is highly ineffective; basically, you’re dead.

Rabies Vaccination Rules in North Carolina

While it’s great that rabies vaccines save our dogs’ lives should they come into contact with an infected animal, the real reason we require dogs to be vaccinated is to protect people. That is also why we treat unvaccinated exposed dogs as rabid and either euthanize them for testing or quarantine them for 6 months (at your expense).

There is no medical rabies exemption for dogs in North Carolina. All dogs are required to be vaccinated between 12-16 weeks of age, within a year after that, then every 3 years. We give a rabies booster vaccine to vaccinated dogs who have exposure to possibly rabid animals. Proof of previous rabies vaccine by certificate or medical records is required to receive a 3-year vaccine. A one-year vaccine is administered to dogs without proof of previous vaccination. Rabies tags don’t count as proof- they could be for anyone.

Thankfully, rabies vaccination is very safe and effective. We use the Thimerosal-free Imrab vaccines and have not seen a reaction in years, even in dogs who have had reactions in the past. I can’t guarantee that any individual dog will not have a reaction to a rabies vaccine, but I can guarantee we use only the safest vaccines available.

Non-Core Vaccines in Dogs

We administer non-core vaccines to pets with specific risk factors due to their lifestyle. No judgment 🙂

We evaluate each pet’s risk factors and come up with a rational plan to protect them against the diseases that they could be exposed to. So let’s go through the available vaccines.


Lepto is a disease that causes liver and kidney failure in dogs (cats are not affected). It is transmitted through the urine of infected animals, which include cattle, deer, skunks, squirrels, rodents, and opossums. The bacteria can live in puddles and other fresh water for weeks. Leptospira bacteria are prevalent in humid warm environments. Sound familiar, North Carolinians? Dogs are infected when they stand, wade, walk through, or drink from infected water sources. We have vaccinations that protect against 4 serovars (strains) of lepto:  Leptospira canicola, L. grippotyphosa, L. icterohaemorrhagiae, and L. pomona. Unfortunately, other serovars can infect dogs and we don’t have a vaccine against them. There is no cross-protection between serovars.

Lepto can also infect humans. While it is unlikely that you would wade in your dog’s pee, you can certainly walk through the same infected puddle as your dog. Luckily, lepto is easily treated with the proper antibiotics. The problem is that sometimes the infection causes liver and /or kidney failure rather quickly, and the dog could be euthanized due to the cost of treatment and severity of the disease. Plus, liver and kidney failure are not fun for anyone. Because of the prevalence of the carriers in this area, most dogs are susceptible to lepto and I recommend vaccinating most dogs.

Lepto Vaccine Rumors and Falsehoods

Back in the day, the lepto vaccine could cause serious vaccine reactions. We’ve been using recombinant vaccines for a long time, and have (knock wood) not seen a serious reaction in years. Certain “breeders” (puppy pimps, not real breeders) have been saying that we should never vaccinate a dog against lepto. They say their breed is more susceptible to vaccine reactions than others. They say that lepto isn’t a real threat and the vaccine is worse than the disease.

They’re wrong. I’ve seen multiple dogs die from lepto, yet not a single dog die from the vaccine. In fact, my vaccine (Recombitek by Boehringer Ingelheim ) has not caused any serious reaction in the 10 years that I’ve been using it. The vaccine just stings a bit while being vaccinated. Secondly, dogs are dogs. While certain individual dogs may react badly to a particular vaccination, there is no breed of dog in which every individual reacts badly to a particular vaccine. No matter what the puppy pimps have told you. I promise.

My dogs are vaccinated against lepto every year. Any dog that has access to standing water in this area should be vaccinated. You can read more about leptospirosis hot spots here.

Leptospirosis in dogs probability map. Lee County, NC is marked with a tiny x. We are in the yellow zone, meaning about 1/6th of dogs tested will be positive for leptospirosis. The Appalachians are a hot zone for leptospirosis.

Canine Enteric Coronavirus

The canine coronavirus vaccine is a vaccine looking for a disease. Canine enteric coronavirus causes the mildest possible diarrhea- sometimes. Most infections are inapparent, you’d never know a dog has it. I’m honestly not sure why any manufacturers still make this vaccine. You can find the coronavirus vaccine in some combination canine vaccines. Nobody recommends this vaccine, it’s completely unnecessary.

Note: this is not the same coronavirus that causes COVID, and vaccination will not prevent COVID infection in your dog.

Kennel Cough

Kennel cough, or more appropriately, canine infectious respiratory disease (CIRD) is an illness caused by over 12 different viruses and bacteria. CIRD is spread by the respiratory droplets (coughing, sneezing, sputum) of infected animals. It causes coughing as you’d guess from the name, usually mild and self-limiting. However, in some individuals, it can be quite serious and progress to pneumonia. One cause of CIRD is the canine distemper virus, which can be very serious!

There are vaccines for a few of the infectious organisms that cause CIRD: canine distemper virus, canine parainfluenza, canine influenza viruses H3H8 and H3N2, canine adenovirus-2, and Bordetella brochiseptica. We vaccinate all dogs against canine distemper virus. We also vaccinate all dogs against canine adenovirus-2 with the modified live injectable product to protect against canine infectious hepatitis, but that doesn’t help protect against CIRD. Our intranasal “kennel cough” vaccine includes Bordetella brochiseptica, canine adenovirus-2, and canine parainfluenza. We also have an injectable canine influenza vaccine that protects against both strains. None of these vaccines produces sterilizing immunity except the canine distemper vaccine. However, the vaccine reduces the severity of the disease should the dog be exposed to any of those particular infectious organisms. And of course, every dog can be sickened by the causes of CIRD that we don’t have vaccines for.


Not every dog that coughs has kennel cough, and kennel cough can progress to pneumonia in some individuals. Coughing can also be due to lung cancer, heart failure, collapsing trachea, allergies, and numerous other serious conditions.

Any dog that is coughing and is also panting excessively or struggling to breathe (hassling for you Southerners), lethargic, not eating, or otherwise not acting normally needs to be seen by a veterinarian right away.

Kennel Cough Vaccine

We recommend the intranasal kennel cough vaccine to any dog that is exposed to non-household dogs in a closed environment for any period of time. That includes grooming, training, boarding, and indoor competition (conformation, agility, etc.). The duration of immunity for the intranasal vaccine is 12 months. However, there are facilities that require the vaccine every 6 months. Unfortunately, that means we have to over-vaccinate your dog. Some facilities do not require the kennel cough vaccine (especially some groomers) but we think it’s a good idea to vaccinate dogs that go to the beauty parlor.

We like the intranasal vaccine because it is protective within 3 days and your dog only needs one dose. There is an oral Bordetella brochiseptica vaccine that is also very effective, but it only protects against that one bacterial cause of CIRD. There is also an injectable Bordetella bronchiseptica vaccine that requires 2 vaccines given 3 weeks apart, and the dog isn’t protected until a week after the second vaccine. All types of kennel cough vaccines must be administered annually.

Canine Influenza Vaccine (H3N2 and H3N8 combined)

Canine influenza (both strains) has sporadic outbreaks all over the US and elsewhere. It’s not nearly as common in our service area as other causes of CIRD- for now. I definitely recommend vaccinating dogs who travel for canine events. There are some local facilities that require the bivalent canine influenza vaccine for boarding, grooming, or hospitalization. IMHO, any dog at risk for kennel cough is also at risk for Canine Influenza and should be vaccinated.

Lyme Disease

The tick-transmitted bacteria Borrelia burgdorferi causes Lyme disease. The most common symptom in dogs is shifting leg lameness due to sore joints. In extremely rare cases (<2% of infected dogs) for reasons we don’t understand, some dogs get Lyme Nephritis. Lyme Nephritis is a very serious kidney disease causing the loss of protein in the urine which eventually can kill the dog. Lyme Nephritis affects Golden and Labrador Retrievers more than other breeds. In dogs, we don’t see the same devastating long-term effects of Lyme disease as in humans. Lyme disease continues to spread across the US and Canada. While it is not yet common here, I’m sure that day is coming. There is definitely a greater risk in the western areas of NC.

Prevalence of Lyme Infection in Dogs in NC 2022
Lyme Disease in Dogs in NC 2022 from CAPC

Some local veterinarians are routinely testing dogs for Borrelia antibodies using a 4dx test. Here’s an interesting factoid: 90-95% of dogs who test positive for Borrelia antibodies will never develop any symptoms of Lyme disease. There is no reason to perform additional tests nor to treat an asymptomatic dog. They can’t get better from a disease they don’t have. Once infected, an individual is always infected, even with antibiotics. Neither treatment nor vaccination prevents the development of Lyme Nephritis. In fact, 30% of dogs that have Lyme Nephritis have been vaccinated against Lyme disease.

We do not carry the Lyme vaccine because there is no proof that the vaccine prevents Lyme disease. That would be very difficult to prove since less than 10% of infected dogs show any signs of disease! The best way to protect your dog against Lyme Disease is with excellent year-round tick control. Tick control also prevents Rocky Mountain Spotted Fever, Ehrlichiosis, Anaplasmosis, Babesiosis, Bartonellosis, and other serious diseases that are much more common here in NC.

Rattlesnake Vaccine for Dogs

One company makes a conditionally licensed rattlesnake vaccine for dogs. Conditional licensing means that the manufacturer is still trying to prove to the FDA that the vaccine is safe and that it works. There are Timber rattlesnakes, Eastern Diamondback rattlesnakes, and Pygmy rattlesnakes in North Carolina. Regardless of vaccination status, rattlesnake envenomation is no joke, and you should take your dog to an emergency vet immediately if bitten. Here’s a great website that shows the snakes common in NC. Look out for the Family Elapidae and Family Viperidae!

The rattlesnake vaccine does not protect dogs against copperheads or cottonmouths (aka water moccasins), which are much more common here in central NC. The vaccine can cause some serious reactions. Some veterinarians think that vaccinated dogs bitten by rattlesnakes have worse symptoms than unvaccinated dogs. We’re not going to recommend this vaccine until or unless the issues are resolved.

Core Cat Vaccines

The cat core vaccines are feline viral rhinotracheitis, calicivirus, panleukopenia, and of course rabies. Rabies is 100% fatal in cats, and panleukopenia is also quite deadly. Feline viral rhinotracheitis and calicivirus are not typically fatal, but they can cause lifetime disease. Once infected, cats are permanent carriers and can easily transmit these viruses to other cats.

Feline Viral Rhinotracheitis

Feline Viral Rhinotracheitis is caused by feline herpesvirus-1, which is why I call it The Herp. This herpes virus is NOT contagious to people. However, it is super-contagious to other cats. Unfortunately, vaccination is not 100% effective in preventing infection, but it does dramatically reduce the severity of the disease.

The Herp is one of the major causes of upper respiratory disease in cats. Affected cats get thick discharge from the eyes and nose, and sometimes develop pneumonia. They can get painful corneal ulcers and in severe cases even lose their vision if left untreated. Once infected, cats can show these signs at any time in their lives, especially during times of stress. Cats can also shed the virus in respiratory secretions (saliva, nasal discharge, eye discharge) whenever they are showing clinical signs throughout their life.

Herpesvirus conjunctivitis in a young cat, from Veterinary Partner

There is no cure for The Herp. Some medications such as Famciclovir or L-Lysine may reduce the clinical signs and prevent recurrence (maybe).


Panleukopenia means “no white blood cells.” This is a highly unfortunate situation because white blood cells are the body’s first line of defense against bacterial and other infections.

Panleukopenia is caused by feline parvovirus. Cat parvo can infect dogs but at this time, dogs do not get sick from feline parvovirus. However, cats can get sick from canine parvovirus. In fact, all parvoviruses were originally feline parvovirus! The canine parvovirus-2 that afflicts dogs now is a highly mutated feline parvovirus.

Kittens that get parvovirus rarely show bloody vomiting and diarrhea which is the hallmark of the canine disease. They just drop dead from sepsis because they don’t have any white blood cells to fight infection from the bacteria in the environment. That’s why they call it panleukopenia; the disease comes from the lack of white blood cells.

Panleukopenia can progress extremely quickly. I know clients who had perfectly healthy kittens in the morning, eating and playing, normal stools in the litter box, and came home from work that evening to mostly dead kittens. It is very difficult to successfully treat septic kittens, even if you can get them to a vet in time.

Just like with canine parvovirus, there is no cure for panleukopenia. We give IV fluids, antibiotics to treat secondary infections, and often blood transfusions to help the cat recover. Even so, about 90% of kittens will die from the disease.


Calicivirus also causes upper respiratory disease in cats, though it is much more severe than viral rhinotracheitis. Infected cats tend to get oral ulcers, making them too painful to eat, as well as the same symptoms as The Herp. Like The Herp, cats infected with calicivirus are infected for life and can shed the virus at any time. It is also high contagious to other cats. Unfortunately, the vaccine does not fully protect the cat, but dramatically reduces the severity of clinical signs. We treat calicivirus similarly to The Herp, and there is no cure.

Severe upper respiratory infection in a cat, from Veterinary Partner

Rabies in Cats

While dogs are the biggest rabies threat to humans worldwide, cats are the most commonly infected domestic animal in the US. In North Carolina, 15 cats tested positive for rabies in 2020.

All cats, regardless of whether they go outside, are required to be rabies vaccinated in North Carolina. The same vaccination rules apply to cats as dogs.

For cats, we use only the PureVax rabies vaccines because they are non-adjuvanted. There are separate one-year and a 3-year versions of the vaccine, unlike the dog vaccine, which is the same either way. We will never give a cat an adjuvanted vaccine.

Non-Core Vaccines in Cats

Feline Leukemia

Outcomes of feline leukemia infection in cats
Possible outcomes of FeLV infection from Veteriankey

Feline Leukemia Virus (FeLV) is a terrible immunosuppressive and cancer-causing virus. Most cats die within 3 years of diagnosis, though a few live a normal life. It depends on the cat’s immune system, how well they fight off the initial infection. FeLV transmission occurs through the saliva of infected cats, and spreads by the sharing of food and water bowls, litterboxes, and by mutual grooming. Infected queens pass FeLV to their kittens in the womb.

We think of FeLV as the “nice cat” disease, because it requires close personal contact for a cat to get infected. However, the virus doesn’t live for very long in the environment. That is why simply going outside is not a huge risk- they have to be persistently closely exposed to infected cats.

We test all kittens and new cats for feline leukemia and FIV unless they have had a negative test in the past. Vaccination doesn’t cure FeLV, so there is no point to vaccinating an infected cat.

Vaccine Recommendations

When a kitten owner is positive that they are going to keep their kitten indoors, we don’t vaccinate against FeLV unless they have an infected cat in the home. Kittens are highly susceptible to feline leukemia infection. If there is a chance that a kitten will be going outside, or if the owner has a habit of taking home stray cats, we’ll vaccinate those kittens. They need a series of 2 vaccines, given 3 weeks apart. We booster the vaccine a year later, and then again 2 years after that if there is continued exposure.

There is very little risk for any healthy adult cat becoming infected with feline leukemia, even without vaccination, and even with constant exposure to affected cats. Here’s a study on that subject in PubMed. For that reason, we rarely vaccinate healthy cats over the age of 3 even if they are going outside.

Chlamydophila felis (sometimes called Chlamydia psittaci)

Chlamydiosis in cats is also called feline pneumonitis, but Chlamydophila usually just causes mild conjunctivitis. It is spread by direct contact and during birth to an infected queen. The bacteria do not last in the environment for long at all, and the disease is rarely seen except in overcrowded unsanitary conditions. The vaccine itself causes soreness, lethargy, and decreased appetite, so is not generally recommended unless the infection has been confirmed in housing. The vaccine doesn’t provide complete protection, either. Shelters often vaccinate against Chlamdophilia but rarely do good pet owners need this vaccine for their cats.

Feline Bordetella bronchiseptica

Yes, cats can get vaccinated against Bordetella also. Bordetella causes the same problems in cats as it does in dogs. Younger cats are more at risk for severe disease and pneumonia. Transmission is through direct contact or respiratory secretions, just like in dogs. And it can be transmitted between cats and dogs. While your typical house cat does not need this vaccine, cats who are boarded, shown, or live in crowded housing situations will benefit. The vaccine is intranasal just as in dogs, and rarely causes any side effects.

Vaccine-Associated Sarcoma in Cats

Vaccine-Associated Sarcoma (VAS) is an often fatal but always devastating adverse effect of vaccinating cats with adjuvanted vaccines. Adjuvants are chemicals added to killed vaccines only that cause the immune system to react properly to the vaccination. Without adjuvants, killed vaccines would not work.

Despite the HUGE surgery, this cat will probably die without radiation and chemotherapy also. See NC State’s current treatment recommendations for VAS.

To mitigate the effects of VAS, we vaccinate cats as low as possible on their limbs. That way, if they develop VAS, we can amputate the leg and potentially save the cat’s life. Some veterinarians are still administering vaccines between the shoulder blades. That makes it nearly impossible to remove the entire tumor if it develops. That being said, chopping off a leg because of a vaccine is certainly a terrible outcome!

Thankfully, Boehringer Ingelheim (previously Merial) makes the PureVax line of feline vaccines. None of these vaccines contain any adjuvants. While VAS is rare, the risk increases 10x by using adjuvanted vaccines vs non-adjuvanted vaccines. Since all the feline vaccines are available without adjuvants, there is absolutely no logical reason to ever use an adjuvanted vaccine in a cat.

Yes, PureVax vaccines are expensive. The 3-year feline PureVax rabies vaccine costs over $30 per dose, compared to less than $4 for Imrab-3 TF, which is labeled for use in cats. The killed FeLV vaccine is also significantly less expensive than the PureVax version. For that reason, some veterinarians choose to risk VAS and use killed adjuvanted vaccines in cats. I honestly don’t know how any vet could live with themselves if they gave a cat cancer when it could have been easily avoided.

Core Vaccine Administration

In both dogs and cats, rabies is required at 12-16 weeks of age, within a year, and then every 3 years after that. There are no exceptions for rabies vaccination in North Carolina. Unvaccinated pets can be euthanized for rabies testing or quarantined for up to 6 months at your (significant) expense. Titers are not an acceptable alternative to vaccination in North Carolina. Rabies is usually given separately from the other vaccines but I’ve seen some combination products for cats.

DAP (distemper, adenovirus-2, and parvovirus) is the most basic core vaccine combination. Some manufacturers combine non-core vaccines with DAP, especially parainfluenza to create the DAPP vaccine. I’ve seen also 4 lepto serovars, lyme, and/or coronavirus stuffed into the same single vaccine, often called a 6-way, 8-way, or some other number-way.

The cat combination product is called FVRCP (feline viral rhinotracheitis, calicivirus, and panleukopenia), or sometimes the feline distemper combination. Why they call it the feline distemper combination is beyond me. The vaccine includes protection against feline parvovirus but for some reason, it’s not called the parvo vaccine in cats. There is no such thing as a feline distemper virus. Don’t blame me, I didn’t make up the names!

We administer DAP and FVRCP on the same schedule. Starting at 6-8 weeks of age, we vaccinate the puppy or kitten every 3 weeks until they are at least 18 weeks of age. This gets around maternal antibody interference. If you’re not familiar with maternal antibody interference, check out our post on vaccinology! About a year later, we give another DAP or FVRCP vaccine. At that point, the vaccine is good for life.


Over-vaccination by too frequent administration of necessary vaccines

Yes, you read that correctly. When we administer a DAP or FVRCP vaccine to a healthy adult dog or cat, that pet is as vaccinated as they will ever be. These vaccines stimulate the immune system extremely well, causing the production of a lot of memory cells. Memory cells spring into action as soon they encounter the pathogen to immediately produce antibodies and destroy infected cells. You can’t make the pet more immune by vaccinating it more often. If the pet is a non-responder, it’s not going to respond to any vaccines, no matter how many we give it.

I know it’s weird that giving up to 5 core vaccines to a puppy or kitten is not over-vaccination, but giving any core vaccine to a healthy adult dog or cat after the year booster is. The reason is science. Again, I invite you to read our post on vaccinology.

Reasons Some Veterinarians Administer Vaccines Too Frequently

You’ve probably heard that the DAP and FVRCP vaccines are good for 3 years. Why do some veterinarians repeat these vaccines every 3 years if the immunity lasts a lifetime? That is an excellent question! I’ve asked some of my colleagues about this, and I’ll share their responses.

Parvo is Scary

That is absolutely true. Many of my colleagues were veterinarians in the 1970s when feline parvovirus mutated into what we now call CPV-2 (canine parvovirus type 2). At that time, there were no vaccines against parvo in dogs, because parvo didn’t infect dogs in the past. When parvo hit, puppies and dogs died. We’re talking hundreds of thousands of dogs, spewing bloody vomit and diarrhea and then dying. It was absolutely devastating.

After the development of the parvo vaccine, veterinarians could finally prevent this terrible disease. While the canine distemper vaccine had been commercially available for years at this point, it wasn’t until parvo hit that manufacturers started recommending annual vaccinations. As far as I can tell, there was no scientific basis for that recommendation. However, veterinarians and pet owners alike were eager to ensure protection against this horrible disease. I guess nobody thought to test the DOI for any longer than a year until the late 1990s.

AAHA’s Canine Vaccination Guidelines

In 2003, The American Animal Hospital Association (AAHA) released its first Canine Vaccination Guidelines, recommending that we administer the core vaccines every 1-3 years. This recommendation shook the veterinary industry to the core. I am ashamed of the behavior of many veterinarians during this time, who ridiculed, mocked, and got angry at the scientists on the task force. One of those scientists, Dr. Richard Ford, was a professor in my veterinary school. I talked with him about his experiences in the task force. He said the 3-year recommendation was a compromise based on politics alone. It had absolutely nothing to do with the science available even at that time, which suggested a much longer DOI for the core canine vaccines. DOI challenge studies- the best kind of studies you can do to prove vaccine effectiveness- were showing immunity for 5 years. We’re at 12 years now!

Even so, when I graduated from vet school in 2008, many practices were still administering core vaccinations annually. Sigh. The brand-new 2022 AAHA Canine Vaccine Guidelines were just released, and for unknown reasons, they have reverted back to 3-year vaccines. I suspect the following has occurred….

Get To The Money!

Don’t act surprised. Most rules and protocols that have no basis in reality or science exist solely because someone is getting rich from the situation.

Back in the day, veterinarians relied on vaccines to bring clients to their businesses at least once a year. Veterinarians envisioned dollars flying out the door because clients wouldn’t come into the clinic if vaccines weren’t due. It was so bad that some vets started splitting and rotating the core vaccines so that dogs got a distemper vaccine one year, a parvo vaccine the next, and a rabies vaccine the 3rd year. Instead of educating the public about the importance of the exam, they chose to dupe pet owners into coming in yearly for a vaccine.

Of course, veterinarians were also quick to spin the problem. To make a clear point of it, veterinarians claimed that pet owners were basically too stupid to understand the importance of an exam. Now, I have to ask why they would say such a thing. I mean, I go to the doctor at least once a year for my exam, and I can’t even remember the last time I needed a vaccine (COVID notwithstanding). If there is value in what you do, explain it, and people will make their own judgments.


A lot of vaccine clinics push over-vaccination because their packages are too rigid. For example, the PetVet clinics at Tractor Supply have a “Vital Package” that includes the core vaccines plus lepto and bordetella. It’s significantly cheaper than getting the exam, parasite screening, heartworm test, lepto, and bordetella vaccines (assuming the dog needs lepto and bordetella) separately. So if a pet parent takes their dog to the PetVet clinic every year and purchases the cost-effective “Vital Package,” the dog is significantly over-vaccinated against DAP. Our wellness bundles include any and all vaccines, to be determined after discussion with you based on lifestyle risks. No risk of over-vaccinating with us!

They Don’t Believe the Science

This one makes me very sad. I was having a discussion with other vets about the duration of immunity studies. Challenge studies- ones where they take vaccinated animals and directly expose them to the pathogen against which they were vaccinated- are the gold standard type studies. For the canine core vaccines, we have challenge studies that prove 95% of dogs are protected against distemper, parvo, and adenovirus-2 for 12 years after the last vaccination. When I say “protected” I mean these dogs are not even infected 12 years after their last vaccine.

If you’re following along, you want to know what happened with the other 5%, right? These are vaccine non-responders. Some individuals, for reasons we don’t understand, simply fail to adequately respond to vaccination. This happens in every species and with every vaccine. A dog could respond great to a parvo vaccine but mount absolutely no immune response whatsoever against distemper. You never know.

The thing about it is that vaccinating a non-responder again doesn’t change anything. You could vaccinate a non-responder yearly, monthly, weekly or even daily and that individual is still going to be susceptible to disease.

Therefore vaccinating all dogs more frequently than once every 12 years will not change anything for the 5% who don’t respond to vaccines. It sucks, but it’s true. What makes me sad is that supposed scientists don’t understand this fact. They think they are going to magically make these non-responders suddenly mount an immune response when in fact nothing will do that.

More Frequent Vaccines Equals More Protection

That’s a nope. The immune system is an all-or-nothing system. I hear a lot of vets say that an individual pet has an increased risk for a particular disease therefore they should be vaccinated more often. The immune system doesn’t work that way. The pet is either protected or not. Administering more vaccines won’t change anything.

Over-Vaccination by Unnecessary Vaccination

Besides vaccinating too frequently, the other way that pets can be over-vaccinated is if they receive vaccines they don’t need at all. For example, some veterinarians are vaccinating all cats against feline leukemia, even adult cats who will never be exposed to this virus. Or their FVRCP core vaccine also contains the Chlamydiophila vaccine, which the vast majority of pet cats do not need. Some boarding or grooming facilities require leptospirosis vaccination regardless of the dog’s actual exposure risks.

The rigid bundling of services can also cause over-vaccination in pets. Your pet may need one non-core vaccine, but not ALL of them. Yet it could be more cost-effective to purchase a bundle with more vaccinations than your pet needs. This increases the risk for adverse effects. And it makes it difficult to know which vaccine caused the adverse effect so you can avoid it in the future.

Unfortunately, there is little that one vet practice can do to change the requirements of another business. However, if pet owners stop using the facilities that require over-vaccination, and tell them why they have switched, we may be able to change their protocols for the benefit of all pets.

Rational Vaccine Schedules

I’ve given you science-based vaccine schedules below. The first rabies vaccine is always good for up to 1 year, and each subsequent rabies vaccine is good for 3 years in North Carolina. You must provide a certificate or other proof of previous rabies vaccination in order for the vaccine to be good for 3 years. Tags are not proof, they could belong to anyone.

The intranasal and oral kennel cough vaccines do not require an initial vaccine series. The rest of the vaccines require at least 2 vaccines given 2-4 weeks apart, to stimulate good immunity. Dogs need annual lepto, kennel cough, lyme, and canine influenza vaccines. You may have to restart the initial series if the vaccine is overdue.

I prefer to separate some of the non-core vaccines by at least 3 weeks to reduce the malaise associated with vaccines. We must separate vaccine administration by at least 2 weeks to insure the immune system mounts appropriate responses, even if we are giving different vaccines.

Dog Vaccines

Age of DogVaccines (non-core in parentheses if needed)
6-8 weeksDAP, intranasal kennel cough
9-11 weeksDAP
12-14 weeksDAP, Rabies
15-17 weeksDAP (Lepto)
18-20 weeksDAP (Lepto)
22-24 weeks(Lyme, Canine Influenza)
25-27 weeks(Lyme, Canine Influenza)
1 yearDAP, Rabies (Kennel cough, Lepto)
1 year 3 months(Canine Influenza, Lyme)
Annually(Kennel cough, Lepto, Canine Influenza, Lyme) Split vaccines
Every 3 yearsRabies

Cat Vaccines


The PureVax Rabies vaccine comes in a 1-year and a 3-year version. Not all practices carry the 3-year PureVax Rabies vaccine. If that’s the case, your cat needs the 1-year PureVax Rabies vaccine every year.

Age of CatVaccines (non-core in parentheses if needed)
6-8 weeksFVRCP
9-11 weeksFVRCP
12-14 weeksFVRCP, Rabies (using the PureVax 1-year non-adjuvanted Vaccine)
15-17 weeksFVRCP (FeLV)
18-20 weeksFVRCP (FeLV)
1 YearFVRCP, Rabies (FeLV)
3 Years(FeLV)
4 YearsRabies
Every 3 yearsRabies


Our goal with vaccinations is to protect dogs and cats from the diseases for which they have risk while minimizing their stress and possible adverse events. Our science-based vaccine schedule ensures pets receive the vaccines they need no more often than necessary.

Unfortunately, we can’t control what other facilities require. Sometimes we have to over-vaccinate your pet with unnecessary vaccines, or with necessary vaccines administered too often. You have the option to use facilities that have rational science-based requirements if you can find them. We’re more than happy to explain to any facility why our DAP and FVRCP vaccine due date is 20 years from now (our practice management system requires a due date). The more pet owners who demand scientific vaccine schedules, the sooner the profession will catch up with us!

Feel free to ask questions or comment below.

14 thoughts on “Preventing Unnecessary Over-Vaccination in Dogs and Cats”

  1. What about titers? Veterinarians get a rabies vaccine when starting vet school….and never get them again. Their immunity lasts. Why then should we be vaccinating our animals every year or even 3 years? A titer showing the required immunity should override the necessity for more vaccines.
    Veterinarians need to learn this, advocate and teach owners and stop over vaccinating our pets. Sadly, the income from regular vaccinations are the bread and butter of many clinics, so this approach is not looked upon favorably. Owners and vets need to advocate more for the health of animals as opposed to the profit from vaccines.

    1. Excellent questions E Smith!

      Titers measure antibodies. Antibodies are great, but they decrease over time if the individual is not exposed to the antigen again. Long-lasting protection comes from cell-mediated immunity. Unfortunately, we don’t know how to measure cell-mediated immunity. In other words, an individual could have undetectable levels of antibody, but still be protected against disease due to memory cells.

      A positive titer means the individual is most likely protected, but a negative titer doesn’t necessarily mean the individual needs to be vaccinated again. I’m not going to change what I do based on an antibody titer for distemper or parvo in a dog that has been vaccinated as a healthy adult. So there is no reason for me to run an antibody titer. BTW, it’s an expensive test, compared to vaccination, and I’d make a lot more money selling titers instead of vaccines. But I have this thing against duping the public that prevents me from adopting such a protocol.

      The difference is the type of vaccines and how they stimulate the immune system. Killed and recombinant vaccines are great at stimulating antibody production but not as great in stimulating cell-mediated immunity. Modified live vaccines- like for distemper and parvo- are great at stimulating cell-mediated immunity because they replicate within the host. Rabies vaccines are killed (human and most other rabies vaccines) or recombinant (PureVax), but not modified live. So all we really have is antibody protection. For rabies, we are pretty confident in the antibody level required to confer immunity, in humans at least (we guessed for animals). For the other vaccines, not so much, unless the vaccine manufacturer bothered to do studies. The only disease that manufacturers legally have to prove efficacy for is rabies.

      Speaking of which, veterinarians are supposed to get rabies titers every 2 years. Not never.

      Thank you for your questions and comments, those are good ones!

      1. I’m not sure this clarified why with rabies it’s recommended that humans get titer tests every 2 years while the recommendations for dogs is a vaccine every 3 years. If they’re both the same type of killed or recombinant vaccine, I would think the vaccine recommendation for animals would be the same as for those administering them. Is it because it’s more expensive to test rather than vaccinate a dog? Is it because we guessed at the rabies antibody levels for dogs but know with humans? It seems the best recommendation for animals would be a titer test every 2 years and a rabies vaccine booster recommended as a more affordable alternative to insure immunity (knowing it comes with potential risk of over-vaccination, which is overall less harmful than contracting rabies). This seems like it would protect animal health while still mitigating human infection. Is a rabies titer a scientifically viable indicator of rabies immunity for animals? If not, then why do we have them at all? If it is viable why would a vaccine be recommended instead? I’m still a bit confused here, and I’m trying to understand. My vet just convinced me to get the vaccine for my dog over the titer because it is legally viable proof while a titer is not. I know legally the benefit outweighs the potential risk of euthanasia, but I’m still trying to figure out what is best scientifically. Thank you for taking the time to address this topic.

        1. The problem with titers is that we don’t know what level will protect every individual from infection. Even if we did know that, a protective titer today doesn’t guarantee a protective titer tomorrow. A titer is only good for the moment the test is run. It is not predictive for any point in the future. It’s probable that host factors such as unrelated illnesses, medications (certainly immunosuppressive medications), starvation, etc. also play into whether or not the individual is protected despite a “good” titer.

          That is the reason that even vaccinated humans receive 2 post-exposure vaccinations. Nobody checks your titer level first if you are potentially exposed to a rabid animal. The risks are simply too high.

          As far as cost, the cheapest titer test, which says negative or positive, is about the same as the price of a rabies vaccine. The ones that give you an actual number cost 3-5 times more than a vaccine.

  2. My dog died of delayed anaphylaxis from a rabies vaccine required to register a microchip. He was a healty, very active senior; fast runner, athletic, until one day exactly 14 days after the vaccine, he died from what I believe to be a cytokine response. Our hearts were broken. No one advised us to monitor him for any signs of distress, which he clearly had.
    The worst is the lack of validation, and how dismissive the animal hospital Dr. was at the suggestion that it could have been an immune response and not a supposed tumor, etc. This was a healthy happy dog, who showed no signs of slowing down. I’m not advocating for rabies and I’m not antivax….I think unfortunately people dutifully follow guidelines, and regulations, and don’t question necessity. Thank you. I’m still incredibly sad over this loss.

    1. I’m so sorry for the loss of your dog, Joanna. Vaccines are powerful immune system stimulators and it would be disingenuous at best to say that bad things can’t happen. There is always a risk-benefit analysis that we use to determine which vaccines are administered to any patient. What we know about cytokines, they are released immediately upon antigen stimulation, and symptoms are often most serious at 5-7 days post stimulation. So 2 weeks later doesn’t make sense. However, that doesn’t rule out an immune-mediated vaccine reaction such as immune-mediated thrombocytopenia (IMTP) or immune-mediated hemolystic anemia (IMHA). Having one dog who died from IMTP due to a cephalosporin antibiotic, and treating a few more patients from the same issue, those reactions are rare but incredibly difficult to treat. Without testing, we’ll never know. That said, IMTP and IMHA from medications, including cephalosporins and vaccines, are quite rare, given the number of patients receiving those medications. It just doesn’t make it any easier for those of us who suffered the loss of a beloved pet. That is one reason I use science to determine which vaccines we give and how often to each patient. Unfortunately, the law doesn’t use science, and there are few things I can do to change the laws regarding rabies vaccines. Though I try!

  3. Our beloved 12 yr old toy poodle was vaccinated yesterday with DHLP and died a terrible death within 12 hours. Almost immediately after receiving the vaccination she collasped. We are devastated. We ignorantly followed and trusted our vet’s recommendations for vaccination. It’s with deep remorse and regrets we move forward.

    1. That’s awful, Sandy. I’m so sorry.
      I wonder if your precious dog even needed the vaccine. I’ve had one patient react to a leptospirosis vaccine (the L part in DHLP) but she survived. Obviously we will not be giving that vaccine to her any more. OTOH, I’ve administered thousands of leptospirosis vaccines in dogs with risk factors without any problems. It is terrible when your dog is the one that does have a problem.

  4. It was informative when you explained that core vaccines protect dogs and cats against common diseases. Are certain dogs more prone to contract certain diseases than others? It seems like it would be a good idea to consult with a veterinarian so that you can figure out what vaccinations your pet needs.

    1. Animals that are immunosuppressed by disease or medication are more susceptible to infection from any kind of pathogen. Certain individuals are more at risk to specific diseases because of their lifestyle. A dog that stays in its backyard and has a house call vet and pet sitters and literally never leaves home has zero risk for canine influenza and kennel cough. That same dog may be at much higher risk for leptosporosis though.

      A good veterinarian evaluates your individual pet’s risks and develops a tailored preventive care plan to dramatically reduce those risks. Simply vaccinating every animal with every available vaccine only increases the risk of a vaccine reaction and does nothing to protect the pet. Vaccinating an already immune pet again and again does nothing to reduce their risks. That’s why I don’t vaccinate dogs against distemper and parvo after their first year vaccine. They’re already immune. I can’t make them more immune.

  5. Quote from your article: “We use the Therminosol-free Imrab vaccines..”
    Did you, by any chance, mean “Thimerosal”?
    I would think you did…. does anyone knowledgeable read the copy before publishing? I would like to trust your publications, but if nobody catches this kind of mistake, then I wonder how serious all this is being taken here?
    I despise intellectual and professional sloppiness! Really. Especially when it is published for all to learn from!

    No hard feelings,

    1. Yes, I did mean Thimerosal. I’m a DVM writing my own original copy. I don’t have an editor. It has been corrected. I’m so glad that you took the time out of your righteous indignation to point out this minor misspelling. Please accept my sincere apologies. Dr. Meghan

      1. Sure Chelsea, thank you for asking. I’m going to be including references in future articles. You’ll notice that we’ve know about extended duration of immunity for a long time.

        Schultz RD, Thiel B, Mukhtar E, et al. Age and long-term protective immunity in dogs and cats. J Comp Pathol 2010;142(suppl 1):S102–8.

        Pollock RV, Carmichael LE. Maternally derived immunity to canine parvovirus infection: transfer, decline, and interference with vaccination. J Am VetMed Assoc 1982;180:37–42.

        Waner T, Naveh A, Wudovsky I, et al. Assessment of maternal antibody decay and response to canine parvovirus vaccination using an enzyme-linked immunosorbent assay. J Vet Diag Invest 1996;8:426–32.

        Wilson S, Stirling C, Thomas A, et al. A new multivalent (DHPPi/L4R) canine combination vaccine prevents infection, shedding and clinical signs following experimental challenge with four Leptospira serovars. Vaccine 2013;31:3131–4.

        Ricardo T, Previtali MA, Signorini M. Meta-analysis of risk factors for canine leptospirosis. Prev Vet Med 2020;181:105037.

        Honsberger NA, Six RH, Heinz TJ, et al. Efficacy of sarolaner in the prevention of Borrelia burgdorferi and Anaplasma phagocytophilum transmission from infected Ixodes scapularis to dogs. Vet Parasitol 2016;222:67–72.

        Krämer F, Hüsken R, Krüdewagen EM, et al. Prevention of transmission of Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum by Ixodes spp. ticks to dogs treated with the Seresto® collar (imidacloprid10%1 flumethrin 4.5%). Parasitol Res 2020;119:299–315.

        Little S, Braff J, Place J, et al. Canine infection with Dirofilaria immitis, Borrelia burgdorferi, Anaplasma spp., and Ehrlichia spp. in the United States, 2013–2019. Parasit Vectors 2021;14:1–16.

        Purswell EK, Lashnits EW, Breitschwerdt EB, et al. A retrospective study of vector-borne disease prevalence in dogs with proteinuria: Southeastern United States. J Vet Intern Medicine 2020;34:742–53.

        Ellis JA, Gow SP, Waldner CL, et al. Comparative efficacy of intranasal and oral vaccines against Bordetella bronchiseptica in dogs. Vet J 2016; 212:71–7.

        Czerkinsky C, Holmgren J. Mucosal delivery routes for optimal immunization: targeting immunity to the right tissues. In: Kozlowski P, ed. Mucosal vaccines. current topics in microbiology and immunology. Vol. 354. Berlin, Heidelberg: Springer; 2010:1–18.

        Ellis JA, Gow SP, Lee LB, et al. Comparative efficacy of intranasal and injectable vaccines in stimulating Bordetella bronchiseptica-reactive anamnestic antibody responses in household dogs. Can Vet J 2017;58: 809–15.

        Maboni G, Seguel M, Lorton A, et al. Canine infectious respiratory disease: new insights into the etiology and epidemiology of associated pathogens. PLoS One 2019;14(4):e0215817.

        Parrish CR, Voorhees IEH. H3N8 and H3N2 canine influenza viruses: understanding these new viruses in dogs. Vet Clin North Am Small Anim Pract 2019;49:643–9.

        Moore GE, HogenEsch H. Adverse vaccinal events in dogs and cats. Vet Clin North Am Small Anim Pract 2010;40:393–407.

        Vila Nova, B., Cunha, E., Sepúlveda, N. et al. Evaluation of the humoral immune response induced by vaccination for canine distemper and parvovirus: a pilot study. BMC Vet Res 14, 348 (2018).

        Rota, A., Dogliero, A., Muratore, E. et al. Serological survey of canine parvovirus 2 antibody titres in breeding kennels in northern Italy. BMC Vet Res 15, 335 (2019).

        Kruth SA, Ellis JA. Vaccination of dogs and cats: general principles and duration of immunity. Can Vet J. 1998 Jul;39(7):423-6. PMID: 9759509; PMCID: PMC1539523.

        Vaccination Guidelines Group; Day MJ, Horzinek MC, Schultz RD. WSAVA guidelines for the vaccination of dogs and cats. J Small Anim Pract. 2010 Jun;51(6):1-32. doi: 10.1111/j.1748-5827.2010.00959a.x. PMID: 20645435; PMCID: PMC7166980. This has a lot of references for canine vaccines Similar to above for feline vaccines

        Hope that’s enough to get you started!

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