Vaccination And Vaccine Reactions In My Dog And Cat

Ron Hines DVM PhD

Explore the links below for information about the benefits and risks of vaccines when given to your pet in excess:

Science-Based Pet Vaccination For Your Cat & Dog

Vaccines & Autoimmunity   

  One Size Fits All? 



This is an older article. The links above will give you more information. But if you are viewing this article, it is quite likely that your vet sent you a vaccination reminder, your dog, cat or ferret recently received the booster vaccinations and things did not go well. Your dog and cat require their initial puppy or kitten series of core vaccinations and perhaps a booster at one year of age to assure that they are protected from the most common infectious diseases. After that, with every additional booster vaccination, the likelihood of undesirable reactions increases. To be sure, the majority of adult dogs and cats handle those unnecessary vaccines well. But some do 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 the manufacturers. (read here)

Adjuvants are compounds that are added to vaccines in an attempt to increase their effectiveness. Few veterinarians administer them any more because adjuvants appear to increase the likelihood of side effects. Several veterinary vaccine producers offer non-adjuvanted 3-year (or longer)-proven-immunity cat and dog vaccines. Those are the vaccine that I use. They contain none of the adjuvants that may cause cancer or immunological system diseases later in life. An even better choice when available might be an intranasal vaccine which requires no injection. The Boehringer Ingelheim/Merial Purevax® feline leukemia vaccine contains no complete virus and no adjuvants. It uses recombinant canary pox vector vaccine technology. I suggest your pet receive a rabies vaccine that also contains no adjuvants. Even non-adjuvanted injectable vaccines are not risk-free. If your pet has had prior vaccine reactions, persistent or transient lumps at injection sites, or its siblings and parents have, think seriously before having more “booster” vaccines administered.

Approximately 1-4% of dogs and cats will have reactions subsequent to vaccination the rate appears to be less in domestic short haired house cats due to their genetic diversity. Purebred cats are at a higher risk. The percentage goes much higher when leptospirosis protection is included in the vaccine. These 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 allergic reactions. True allergic reactions do not occur when the pet is first vaccinated. They occur on subsequent vaccinations to products that share the same ingredient(s). In my experience, the longer the interval between vaccination and reaction, the less severe the reaction is likely to be. Many of these reactions – perhaps all of them – are due to components added to the vaccine as preservatives. I never suggest that small breeds of dogs or puppies under 5 months of age receive leptospirosis vaccination. The risk of vaccine reaction decreases 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. The more vaccines administered during the same office visit, the more likely reactions are to occur.

When the pet is “not himself” the following day or two, it can be due to nothing more than the stress of the hospital visit. Some pets are more emotional than others and suffer real physical distress due to the fear they experience in the veterinary hospital environment. I see this quite commonly in toy breeds of dogs as well as in herding and high-strung breeds. I also see it more in shy cats. House call veterinarians are sometimes the solution to this type of problem. When owners call back with this problem and 24 hours have passed, I suggest they take their pet’s rectal temperature. If it is between102.6 F (39.2C) and 101F (38.3C) and 12 hours have passed, the problems is probably a post-stress phenomenon that will pass in a day or two without treatment. I am even more assured when the pet is still eating or when it will accept it’s favorite food treats. Soreness at the vaccination site is another common phenomenon – particularly when the vaccine contains a leptospirosis ingredient.

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 or swelling of the face. When severe, this is a medical emergency that can interfere with breathing. A much more severe form (anaphylactic reactions, anaphylaxis) involves a sudden drop in blood pressure and defects in the clotting mechanism of the blood. These are whole-body events affecting many body systems. Anaphylaxis is often life-threatening and demand immediate veterinary attention.

True anaphylaxis does not occur when the pet is given his first vaccination with the products ingredients. The first vaccination, and perhaps first subsequent vaccinations, sensitize certain pets with this tendency. . In these cases, the pet’s “memory cells” take note of vaccine ingredients and release powerful chemicals into the blood (histamine, etc) when the same substance is encountered again. Histamine constricts the small tubes of the lungs making breathing difficult. The stomach and intestines may also be affected causing vomiting and diarrhea. Major histamine release also causes a sudden drop in blood pressure robbing the body of vital oxygen, leading to shock and collapse. The walls of blood vessels then begin to leak fluid (edema) into the lungs and other body organs. Heart rhythm is also affected causing a rapid , weak pulse. These pets appear confused and apprehensive.

Anaphylactic And Anaphylactoid Reactions

Certain ingredients, including  polymyxin , and x-ray dyes can cause similar reactions to anaphylaxis on the pet’s first exposure. This is a different phenomenon based on a toxic reaction to the drugs rather than true anaphylaxis. However, treatment is the same.

Pets with any history of allergic reactions in their past are more likely to have vaccine reactions. The tendency is thought to have inherited causes that are passed down in certain breed lines. That is why I see these problems more often in pure-bred pets.

Anaphylaxis is an emergency condition requiring immediate professional attention. First,an open airway and breathing must be established. Oxygen is often helpful as is temperature and intravenous fluid support. The drugs, epinephrine and antihistamines are our mainstays in combating anaphylaxis. Rapid acting corticosteriod injections may also be helpful.

Future vaccinations for pets that have experienced a true vaccine reaction?

I personally advise that these pets receive no further booster vaccinations. I feel that the danger of subsequent vaccinations outweighs their benefits..

If you feel you must re-vaccinate your pet, consider pre-treatment with antihistamines and corticosteroids. These in no way guarantee that reactions will not occur. Subsequent reactions are often more severe than the previous one. Also 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 a vaccine that contains no adjuvants.

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 revaccinate your pet, consider if the risks outweigh the needs and benefits – But remember, certain properly-timed kittenhood and puppyhood vaccinations are absolutely crucial to your dog and cat’s long term health.

I recently read the results of a study conducted in 2007. (ref) Scientists studied the length of time vaccination immunity ( immunological memory ) persists in humans. We know that the immune system’s memory in all mammals, cats-dogs&people, is very similar. Measles, for example, is a virus very much like distemper of dogs. (ref) The immunity conferred by a two-dose series measles vaccine lasts a lifetime. Vaccina (cow pox), mumps, Epstein-Barr virus, varicella/zoster and rubella also last a lifetime. Tetanus 11, years, Diphtheria 19yrs.

What About Rabies Vaccination?

A legal issue exists regarding periodic rabies immunizations. In some states this 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 your pet. Certainly a pet that roams freely out of doors or that is likely to bite is at more risk of contracting rabies and causing human concern than one that is not. In some principalities, a letter from your veterinarian, explaining the danger of immunizations in your pet may suffice. But you will need to determine if this is the case where you live. I prefer a one-year duration, non-adjuvanted killed rabies vaccine.

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