Vaccination and Vaccine Reactions in Dogs and Cats
Ron Hines DVM PhD
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If you are viewing this article, it is quite likely that your dog or cat recently received it's booster vaccinations and that they 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 to protect them from dangerous infectious diseases. After that, their likelihood of reactions increase. To be sure, most adult pets handle vaccines well. But some do not. When reactions occur, they can be frightening to pet owners and pets alike. The number of dogs and cats that experience those reactions is unknown, but quite likely much greater than what gets reported. (ref1, ref2)
Adjuvants are compounds that are added to vaccines in an attempt to increase their effectiveness. I no longer use them because they seem to have many side effects. At least one company, Intervet , offers a non-adjuvanted 3-year cat vaccine. This is the vaccine that I use in cats. It contains none of the adjuvants that may cause cancer or immunological disease later in life. An even better choice might be Heska's intranasal vaccine which requires no injection. A feline leukemia vaccine containing no complete virus and no adjuvants is Merial's Purevax products which uses recombinant canarypox 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 cat has had prior vaccine reactions, think seriously before having any vaccines administered.
1-4% of dogs and cats will have reactions subsequent to vaccination
the rate appears to be less in domestic shorthaired house cats due to
their genetic diversity. Purebred cats are at a higher risk. The percentage
goes much higher when leprospirosis 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.
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 aprehensive.
Certain ingredients, including poymyin, 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. A brave Texas veterinarians brought this uncomfortable fact into the limelight some years ago (ref). 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 essential.
I recently read the results of a study conducted in 2007. (ref) Scientists studied the lengh of time vaccination immunity (immunological memmory) persists in humans. We know that the immune system's memmory in all mammals, cats-dogs&people, is very similar. Measles, for example, is a virus very much like distemper of dogs. (ref) The immunity confired 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, Diphteria 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 imunizations 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.