Taking the Sting Out of Vaccinations

Laurie S. Coger, DVM, CVCP

Late afternoons are always busy at a veterinary hospital, as people try to make their routine appointments after finishing the day at work. Add in the urgent appointments for people who have come home and found their pet has a problem, and the waiting room fills rapidly. Just when the staff is feeling like the end of the day is in sight, a call comes in. Rocky, the dog that was vaccinated at 5:30 is on his way back, with a badly swollen face, hives, and rapid breathing. A vaccine reaction.

Vaccines have long been used in humans, livestock, and pets, and have saved countless lives. From smallpox to bovine viral diarrhea to rabies, vaccines have protected our pets, our food animals, and us. As new diseases or strains have emerged, vaccines have evolved to stimulate greater immunity in recipients. Vaccines have become more potent, and can produce high levels of immunity with just a single dose.

Vaccines work by stimulating the immune system to develop antibodies and cellular immunity to the disease in question. A vaccine exposes the body to an antigen -- a key part of the disease causing virus, or the actual virus that has been killed or modified so it cannot cause disease. The body reacts to the vaccine in two ways. The humoral side of the immune system produces antibodies, while the cell-mediated side activates white blood cells that attack virus and bacteria infected cells. By producing antibodies which attack disease causing organisms, and activating specific white blood cells that destroy bacteria and virus infected cells, the immune system fights off infections, often before the dog even feels sick.

The crucial part of the immune system that allows vaccination to work is the memory cell. Both the humoral and cellular parts of the immune system produce memory cells. These cells have the "imprint" of the disease-causing organism, for example, parvovirus. Should your dog be exposed to parvovirus after being vaccinated, these memory cells reproduce very rapidly, stimulating rapid antibody production and activation of white blood cells. The end result is that your dog does not get the disease.

It is obvious that vaccination can be very beneficial. However, some individuals may have adverse reactions, to the actual antigen or to the other compounds in the fluid of the vaccine. Common reactions include hives or facial swelling, itching, fever, respiratory distress, vomiting or diarrhea, or swelling and pain at the injections site. These reactions can occur almost immediately, or within days of vaccination. In severe cases, cardiovascular collapse and death can occur. Fortunately these cases are rare.

Rocky, the dog seen at our hospital, was back at the hospital an hour after receiving a vaccination. He was stable on arrival, and the Benedryl his quick thinking owner had given was starting to help. Antihistamines block the release of the biochemical histamine from the stimulated white blood cells. In a vaccine reaction, histamines are responsible for airway constriction, pain, itching, and hives formation.  He was treated with corticosteroids to suppress inflammation and block inappropriate immune system response, as well as further antihistamines. Within an hour, his facial swelling and hives were improving. He was back to normal in 36 hours. However, his reaction brings up the question of future vaccinations, as he is only two years old.

Fortunately for Rocky, our knowledge of vaccines and immunology has greatly progressed in recent years. The days of the yearly "booster shot" are long behind us. The American Veterinary Medical Association (AVMA), the American Animal Hospital Association (AAHA), and most veterinary colleges agree that after an initial puppy series, most vaccines do not need to be given any more frequently than every three years. Some studies have suggested that immunity from commonly used vaccinations lasts seven years or more. There is no benefit to giving an additional vaccination to the dog that already has sufficient immunity. Even more importantly, repeated vaccination has been associated by some authorities with autoimmune diseases, including immediate reactions like Rocky's, destruction of red blood cells or platelets, and hypothyroidism. All of these problems can have a serious or even life-threatening effect on our dog's lives.

Many veterinarians have changed their vaccination protocols, following the recommendations of the AVMA and AAHA. These organizations suggest determining which vaccines are essential or "core", taking into account geographic differences, exposure, previous vaccinations, and effectiveness of the vaccine. Diseases such as parvovirus, rabies or distemper are often considered essential. These vaccines are given in a puppy series, then on a three-year interval as the dog reaches adulthood. Vaccines such as Bordetella (kennel cough) or Lyme are often considered "non-core" and are given on a case-by-case basis. For animals with no exposure, there is no benefit in receiving the vaccine.

Several other canine vaccines are currently available on the market. Among these are vaccines for canine coronavirus and Giardia. Infection with canine coronavirus alone has been associated with mild disease only, and only in dogs < 6 weeks of age. It has not been possible to reproduce the infection experimentally.  The vast majority of dogs respond quickly to treatment for Giardia infection, and most infected dogs are asymptomatic. The disease is not usually life threatening, nor does the vaccine prevent infection. Therefore these vaccines are not recommended.

Several major vaccine manufacturers have responded to the call for longer intervals between vaccinations by proving their products have a three-year duration of action. Currently there are vaccines for distemper, parvovirus, and adenovirus proven to last at least three years. (Anecdotal reports have suggested that for at least one manufacturer, these "three year vaccines" are no different from those labeled for yearly use.) Rabies vaccine has long been documented to last at least three years. The work of the Rabies Challenge Fund previously reported in the Journal is expected to prove a seven-year duration of immunity.

Given that both of the largest veterinary associations, veterinary colleges, and even vaccine manufacturers are recommending extended vaccination protocols, it is bewildering and a bit dismaying to hear of animals receiving vaccines each year. Hopefully this will change as information becomes even more widely more available on the risks inherent in inappropriate vaccination. While some veterinarians are extremely progressive and incorporated extended vaccination protocols years ago, others still recommend yearly vaccinations or non-recommended vaccines.  Whatever the veterinarian's reasons for doing so, keep in mind as your dog's owner, you can either accept or decline any recommendation. It is your right and responsibility to decide what is in your dog's best interest. The only vaccination you are obligated to keep current is rabies. Each state has their own laws pertaining to rabies vaccination of animals, so be sure to check your state's requirements.

So how will you decide which vaccinations your dog will receive, and when should they be given? I start with a basic vaccination schedule (which follows), and modify it on a case-by-case basis for each animal. Changes may be made in our plans as circumstances change, including vaccine reactions such as Rocky experienced. Dogs with vaccine reactions generally never receive vaccination for that disease again, and are carefully monitored with any other vaccines. Depending on the case, blood testing may be used to measure the level of antibodies against disease. While these titer tests are not a perfect measure of immunity, in many cases they show significant antibody levels, years after vaccination. 

The field of veterinary immunology and vaccination has changed greatly in the relatively short time I have been in practice. Early in my veterinary career, I was often confronted with multiple cases of parvovirus in a single day. Sadly, many of these did not survive. In the past year, I a total saw two cases. I believe the reason for this is the effectiveness of our parvovirus vaccines. Conversely, when I began practicing, it was common procedure to give multiple vaccinations at one time, or to vaccinate twice yearly in show and competition dogs. Vaccine reactions were extremely rare. Last year I saw a four-month-old puppy experience a fatal reaction to a distemper combo vaccine, going from tail wagging to death in two hours. It was the second vaccine the puppy had ever received. Non-fatal reactions seem to be more and more common. I believe the explanation for these events is the high potency of our vaccines, coupled with what we now know to be too frequent administration of these products. 

The days of a simple, harmless, "shot" are long gone. We need to view vaccines as powerful chemical and biological agents capable of stimulating the immune system, the body's protector against disease. Used inappropriately, vaccines can trigger excess or misdirected immune system responses, often with serious or fatal results.

Recommended Vaccination Protocol

Age                                                    Vaccine Type                         

10 weeks                                                           Parvovirus

14 weeks                                                           Distemper/Parvovirus only

18 weeks (optional)                                            Distemper/Parvovirus only

24 weeks or older                                               Rabies Vaccine, Thimersol free

1 year post last vaccination                                  Distemper/Parvovirus only booster

1 year post initial Rabies vaccination                   Rabies Vaccine 3 year, Thimersol free.Give at least 4-6 weeks after                                                                          distemper/parvo.

Perform vaccine antibody titers for distemper and parvovirus (if desired) every three years thereafter, or more often. Vaccinate for rabies virus according to state law.

As common sense and good medical practice would dictate, do NOT vaccinate bitches during heat, pregnancy or lactation. Do not vaccinate during times of stress such as: surgery, travel, illness or infection.

Note: The above vaccine protocol is suggested for those dogs where minimal vaccinations are advisable or desirable. This schedule is one I recommend and does not imply that alternate protocols recommended by other veterinarians would be less satisfactory. All protocols may need to be modified for an individual patient and/or situation.

© 2008 Laurie S. Coger, DVM, CVCP. Reprint requests click here.