vaccinationreactions

If you are viewing this article it is quite likely that your dog or cat recently received it's booster vaccinations. We are fortunate that less than 1% of pets receiving these vaccinations have serious reactions. But when they occur, they can be frightening to pet owners and pets alike.

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.

Approximately 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. 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. (JAMA 227:1102-1108).

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.

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.

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.

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Dear Ms. M. I was very sorry to read of your loss. Pets quickly become treasured family members and I am sure this was a horrible experience for you. Buster had an anaphylactic or anaphylactic reaction to one of the ingredients in the Rabies vaccine. Generally, it is not the rabies virus content of the vaccine that causes this. Instead, it is one of the added ingredients used to stabilize the product, increased its effectiveness (adjuvants) or prevent bacterial contamination. The most common culprits are the antibiotics, Gentamycin, Neomycin or Streptomycin. Some vaccines contain gelatin, which has also caused this problem. In other cases preservatives have been implicated. Anaphylaxis is a form of allergy that involves the immune system. Anaphylactoid reactions have the same signs but a different, less understood mechanism. Pets with this tendency appear quite normal. However, with repeated injections, their bodies produce antibodies (IgE) against an ingredient in the vaccine that persist in their blood stream. Although some inexplicable cases of anaphylaxis with no prior exposure do occur, the first one or two reactions that prime the animal are generally unapparent. So I doubt that Buster became allergic to the vaccine on the date it was given. It was almost certainly a previous year's vaccination that set Buster up for this violent reaction (acute hypersensitivity) that occurred. When the antigen (allergen) was again encountered, these antibodies cause the rapid disintegration of pre sensitized mast cells and basophilic - body cells that releases histamines, leukotriene C4, prostaglandin D2, and tryptase. The released of these body chemicals caused the distress you saw in Buster on your way home. The most serious effects are a sudden drop in blood pressure and constriction of the passages in the lungs. Serious anaphylaxis occurs in a matter of seconds or minutes. When I have seen it, the pet usually already shows signs of distress before even leaving my examination room. The longer it takes for the reaction to begin - the milder it usually is. Fear seems to intensify the reaction. It only occurs in a very small percentage of animals. It seems to be an inherited trait. I have seen it more often in purebred pets than in mixed breeds pets. When I am the least bit suspicious that a pet might be prone to an anaphylactic reaction, I give them an intramuscular injection of an antihistamine similar to Benadryl, fifteen minutes prior to administering any vaccine. When anaphylaxis occurs despite this, the pet must receive an immediate injections of epinephrine. Pharmacies sell Epipens that are sold for humans that suffer an acute attack due to an insect sting, or the consumption of certain nuts or peanuts or due to some other allergen exposure. It is also wise to give them a substantial dose of antihistamine when anaphylaxis occurs. Tablets do not work fast enough, so an injection should be given. I prepare a first aid kit for the owners of pets who have this problem so they will have immediate access to these medications when a crisis occurs. If my injections do not stabilize the animal, I put them in a tent with pure oxygen and maintain their normal body temperature. Even then, some pets cannot be saved. Basically, anaphylaxis is due to an error in the pet's immune system, which misidentifies an unimportant protein molecule as a danger to the animal that must be attacked. Once an animal is sensitized to an antigen (allergen) the sensitivity and threat continue throughout life. I know this is no consolation to you. It was no ones fault. It was just a cruel idiosyncrasy of Nature. R.S.H.

Ask the Veterinarian, Veterinary question, Ask the Vet, Veterinary Advice, Dr. Ron Hines.