Vaccination And Vaccine Reactions In My Dog And Cat

Ron Hines DVM PhD

Much Time Has Passed Since I Wrote This Article. Just Follow The Links Below For More Current Information 

A Science-Based Vaccination Schedule For Your Dog & Cat

    Vaccines & Autoimmunity   

  One Size Fits All? 



I wrote this article some time ago. I update it now and then, but the links above will give you more information. If you are reading this, its quite likely that your vet sent you a vaccination reminder or your dog or cat received a booster vaccination and things did not go well. Pets require their initial puppy, kitten an kit vaccination series and a booster at one year of age to assure that they are well protected from common infectious diseases. Vaccine immunity is known to persist a very long time – much longer than antibody titre persists in your pet’s blood stream. (read here) After that, with every additional booster vaccination, the likelihood of undesirable reactions increase. To be sure, the majority of adult dogs and cats will handle those unnecessary vaccines well. But some will not. When reactions occur, they can be frightening to pet owners, veterinarians and pets alike. The number of dogs and cats that experience those reactions is unknown. But it is considerably greater than what gets reported to the USDA or to the manufacturers. (read here)

Adjuvants are compounds that are added to vaccines in an attempt to increase their effectiveness – a wake up call to your pet’s immune system. Few veterinarians administer adjuvanted vaccines any more because adjuvants appear to increase the likelihood of side effects. Most veterinary vaccine producers offer non-adjuvanted 3-year – proven-immunity cat and dog vaccines. These vaccines don’t suddenly stop protecting your pet when the 3 years are up. Its just that the pharmaceutical companies producing them never tested for immunity after three years. Even non-adjuvanted vaccines are not entirely risk-free. If your pet had a prior vaccine reaction, a persistent or transient lump at the injection site, or its siblings and parents have, think seriously before deciding to having more “booster” vaccines administered.

Approximately 1-4% of dogs have reactions subsequent to vaccination. The rate appears to be less in random-bred domestic short-haired cats due to their genetic diversity. Purebred cats are at higher risk. The percentage becomes much higher when leptospirosis is included in a canine vaccine. I never suggest that small breeds of dogs or puppies under 5 months of age receive leptospirosis vaccinations. Reactions range from a day or two of reduced activity and food intake to life-threatening reactions that occur within 30 seconds of vaccine administration. The most serious of these are true anaphylactic reactions. Anaphylaxis is similar to a severe, sudden and violent allergy. It does not occur when a pet is first vaccinated, but that vaccination can prime a pet’s immune system to react to a subsequent vaccination that shares one or more of the ingredients. In my experience, the longer the interval between vaccination and reaction, the less severe the reaction is likely to be.  The risk of vaccine reaction seems to decrease significantly as body weight increases. Dogs weighing 22-99 pounds have approximately half the risk of vaccine reactions when compared with dogs weighing less than 22 pounds such as chihuahuas, toy poodles, dachshunds, pugs and terriers. Dose size might partially account for that. (read here) The more vaccines administered during a single office visit, the more likely reactions are to occur.

When your pet is “not himself or herself” the following day or two, it can be due to nothing more than the stress of the hospital visit. (read here) Some pets are considerably more emotional than others. They suffer real physiological distress due to the fear they experience in a veterinary hospital setting. (read here)  I see fear-based reactions most commonly in toy, herding and high-strung breeds. I also see it in shy cats – although many of these felines internalize their fears rather than putting up a fuss. House call veterinarians are sometimes the best solution to this type of problem. Soreness at the vaccination site is another common phenomenon – particularly when the vaccine contained a leptospirosis ingredient.

More About Anaphylaxis 

As I previously mentioned, the most serious form of post-injection reactions are true allergic phenomena. These involved learned body sensitivity to specific ingredients in the vaccine. Often, it is not the actual virus or bacteria elements within the vaccine but rather preservatives and other ingredients that were added. Of particular concern are antibiotics , thiomersol and gelatin. In my experience, these reactions occur within 30 minutes of vaccine administration – usually within 10 minutes or less. The most common form are hives an swelling of the face. When severe, this is a medical emergency that can interfere with your pet’s breathing. Even more severe forms involve a sudden drop in blood pressure and defects in the pet’s blood clotting mechanism. These are whole-body events affecting many body systems. They demand immediate veterinary attention.

True anaphylaxis does not occur when your pet is given its first vaccination with the products ingredients. The first vaccination or perhaps a subsequent vaccination, sensitize certain pets with this tendency. In these cases, the pet’s “memory cells” take note of vaccine ingredients that on re-exposure result in the  release powerful chemicals into the blood (histamines and other inflammatory compounds). What occurs is called degranulation. Histamine constricts the small channels (bronchioles) within your pet’s lungs making breathing difficult. Your pet’s stomach and intestines can also be affected producing vomiting and diarrhea. Large histamine releases can also causes a sudden drop in blood pressure robbing the body of vital oxygen and leading to shock and collapse. In those situations, the walls of blood vessels begin to leak fluid (edema) into the lungs and other body organs. Heart rhythm can also be affected leading to a rapid and weak pulse (circulatory collapse). 

Anaphylaxis is an emergency situation requiring immediate professional attention. First, an open airway and breathing needs to be established. Supplemental oxygen is helpful as is temperature and intravenous fluid support. Intravenous epinephrine and antihistamines are mainstays of combating anaphylaxis. Rapid acting corticosteriod injections can also be helpful. Treatment of anaphylaxis and its causes do not differ between dogs, cats and humans. (read here)

What If My Pet Experienced A True Vaccine Reaction?

I personally advise that these pets receive no further booster vaccinations. I feel that the danger of subsequent vaccinations outweigh their benefits. But If you feel you must re-vaccinate your pet, consider pre-treatment with antihistamines and corticosteroids. That does not guarantee that a reactions will not occur, but it is the best I can offer. Subsequent reactions are often more severe than the previous one. Do not have more than one vaccine administered on the same day. Note the brand of vaccine that was used and do not use that brand again. Use vaccine that contain no adjuvants. Anxiety can compound side effects so consider having a house call veterinarian administer the vaccine if your pet or you fear animal hospitals. Many veterinarians still recommend that dogs and cats receive vaccinations much too frequently. The protection most vaccines afford lasts for years and some for a lifetime. In Western World, veterinarians have traditionally over-vaccinated pets to generate the revenue that helps supports under-charging for more complex procedures. Before you re-vaccinate your pet, consider if the risks outweigh its needs and benefits – But do remember that properly-timed kittenhood and puppyhood vaccinations are absolutely crucial to your dog and cat’s long term wellbeing.

What About Rabies Vaccination?

A legal issue exists regarding periodic rabies immunizations. In some states a rabies vaccination is required every year. In others every three years. Many three-year vaccines are on the market. There is controversy as to whether three year rabies vaccines are more likely to cause reactions than one year duration vaccines. How you handle this legal issues is a decision you must make for yourself. A pet that roams freely out of doors or that is likely to bite is at more risk of contracting rabies or causing human concerns than one that is not. In some principalities, a letter from your veterinarian explaining the danger of immunizations or a current rabies antibody titre from your pet might suffice. You will need to determine if this is the case where you live.

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