Contact: Tania Banak, 608/263-6914, banakt@svm.vetmed.wisc.edu

Dr. Ronald D. Schultz, a veterinary immunologist at the University of Wisconsin-Madison School of Veterinary Medicine, began researching vaccines more than 25 years ago, when he first wondered why humans were vaccinated as children and then not again, but animals were vaccinated annually. His research confirms that most animal vaccines, like human ones, create long-term immunity. Yet the veterinary profession has been hesitant to change its long-standing practice of annual vaccination. Dr. Schultz provides reasons why change is necessary.

Do we vaccinate animals too often? Yes, if we’re giving all the vaccines available on an annual basis, says Dr. Ronald D. Schultz, a veterinary immunologist and professor and chair of the Department of Pathobiological Sciences at the University of Wisconsin-Madison School of Veterinary Medicine.

His opinion is based on more than 25 years of vaccine research. While he stresses that it’s critical to stimulate initial immunity in animals while they are young, his work has revealed that many vaccines provide lifelong immunity, making repeated vaccinations after the first year of doubtful value. To compound the situation, he has found that indiscriminate vaccination of adult animals can trigger adverse reactions.

“In my opinion, vaccines are used that aren’t needed and certain vaccines are given to animals more often than they need them,” says Dr. Schultz. He maintains that puppies and kittens should receive core vaccines and non-core vaccines should be given only to animals that need them, based on the situation.

“Medically, you can’t justify giving Lyme vaccine to dogs that live in an area where the disease has not been or is rarely diagnosed,” he says.

Though Dr. Schultz’s position is controversial, veterinarians are beginning to realize his position is scientifically correct. For example, a survey of feline practitioners revealed that ever since an increase in fibrosarcomas in the late 80s was associated with feline leukemia and rabies vaccines, more than half of them vaccinate cats once every three years or less for leukemia and once every three years for rabies. This reduces the chances of fibrosarcoma and provides the same immunity as when vaccination occurs annually.

Dr. Schultz feels early core vaccinations of as many puppies and kittens as possible creates a greater immunity within the dog and cat population, reducing the possibility that a disease will spread. In dogs, core vaccines include distemper, adenovirus, parvovirus and rabies. In cats, it is panleukopenia, calicivirus, herpesvirus, and rabies. These diseases are universally prevalent and have the potential to spread throughout a population if animals are not immunized. Therefore, every effort should be made for the owners of pets to get their puppies and kittens vaccinated.

Dr. Schultz feels that if the core vaccines are given at least once to all puppies and kittens over three months of age, the majority of those animals would be protected for a lifetime from the four diseases for which the vaccines are specific. Non-core vaccines, on the other hand, are designed to protect against regional problems and only in animals at risk. Also, many of the non-core vaccines are for diseases with low morbidity and/or mortality.

If the disease prevented by a non-core vaccine is not prevalent in your region, you actually run the risk of eliciting adverse reactions with a product that is not needed. Furthermore, many of the non-core products are not highly effective since they provide short term and limited immunity.

Pet owners are becoming savvy to the risks involved in vaccinating. Veterinarians that have switched to giving fewer vaccinations have not experienced a loss in clientele. In fact, many have experienced the opposite, as pet owners that don’t believe in indiscriminate vaccinations have switched to practitioners that feel the same way.

If We Vaccinate Less, Won’t the Diseases Come Back?

Some veterinarians worry that reducing the frequency of vaccinations will result in a return to the widespread distemper outbreaks that occurred in the 50s and 60s, or the devastating parvovirus episodes of the late 70s and early 80s before vaccines were even available. But Dr. Schultz reassures them that as long as core vaccinations are maintained in young animals, the population will have a general level of immunity, making it impossible for a disease to take hold and spread unchecked. That is the basis of a vaccination program, and with products like the core vaccine, long term immunity is assured.

He notes that booster shots at one year of age are important, just in case the original puppy or kitten vaccine was compromised by lingering maternal antibodies. But after that first year, no further immune benefit is gained by revaccinating the animal at 2, 3, 4 or even 5 years of age with core vaccines. There is an exception not in immunity, but mandated by law for one of the core vaccines, rabies, where once every three years vaccination is the maximum interval allowed between vaccinations.

“The goal for the future should be to vaccinate more animals than are now vaccinated but to vaccinate those animals less often and only with the products that the animal needs if we are to be successful in using vaccines to further reduce or eliminate diseases,” says Dr. Schultz.

Risk of Adverse Reactions Outweighs Benefits of Vaccination in Some Cases

An indoor cat whose life expectancy has just been reduced to 18 months, give or take 6 months, due to vaccine-associated fibrosarcoma would have been better off without feline leukemia and rabies vaccines being given annually. Similarly, Dr. Schultz notes that there came a time when allergic uveitis (blue eye) caused by CAV-1 vaccine was more common than cases of infectious canine hepatitis. He says there are many other examples of adverse events from unnecessary vaccines and/or too many vaccinations.

Dr. Schultz states that practitioners need to weigh the consequences and do what is best for the animals. To avoid over-vaccinating and the potential of unwanted side effects, Dr. Schultz recommends reducing the frequency of core vaccinations to once every three years or less after the animal has received its one-year booster. If necessary, different vaccines can be given each year on a rotating basis.

“Veterinarians need to de-emphasize annual vaccinations and instead stress the importance of heartworm tests, dental maintenance, and a physical exam as a reason for bringing patients in for annual visits,” Dr. Schultz recommends.

Twenty or 30 years ago, animals were rarely given more than three or four vaccines at a time because that is all that were available. Today, there are 16 vaccines available for dogs and a similar number for cats. Veterinarians sometimes give products that contain 8-10 vaccines in the same syringe. Sometimes more than four separate vaccinations are given to puppies before they are a year of age and then these same vaccines are given annually until the animal dies. There is rarely a need for that many vaccines or vaccinations in any animal.

“It’s extreme to vaccinate for everything,” Dr. Schultz maintains. In one of his studies, he found that anaphylactic or adverse allergic reactions occurred at a rate of 1 in 1,000 versus the 1 in 10,000 vaccinations he had expected. The more vaccines are given, the higher the risk of an adverse reaction.

Research is Time-Consuming and Expensive

Doing research on vaccine effectiveness and duration of immunity has not been easy. Funding is difficult to obtain due to the expense of maintaining animals for years. Yet it takes years of follow up to adequately evaluate a given vaccine for its duration of immunity. Vaccinated animals as well as controls must be challenged to compare natural versus vaccinal immunity.

Countless projects later, Dr. Schultz has gained an overview of the big picture. He admits that some vaccines, such as kennel cough, especially the Bordetella bronchiseptica component, are needed annually because they don’t maintain long term immunity and often fail to provide adequate immunity. In all cases, risk/benefit must be weighed. For example, rabies is a risk to humans as well as dogs. That may justify vaccinating a dog more frequently in order to assure that humans are not infected, but if there is a three-year product, the law should not require more frequent vaccination, and the three-year product should not be given annually, only once every three years. Also, animals that have been vaccinated only once for rabies would have a much greater chance of not getting infected than those that have never been vaccinated due to immunologic memory. Dr. Schultz explains that once the immune system sees an antigen, it can remember and respond more effectively the next time it encounters the same antigen.

Also, just because young animals are vaccinated doesn’t mean they’re immune. If antibodies received from their mother were exceptionally strong, the antibodies may have interfered with the vaccine given. That is the reason for the last puppy or kitten dose to be given at or after 12 weeks of age and the reason for the booster at one year, since a small percentage of animals may not respond until after four or more months of age. These animals are genetically low or poor responders.

Avoiding all vaccinations, as a few veterinarians recommend or some owners want, puts the animal at high risk for diseases that can easily be prevented with core vaccines. “Initial immunity via vaccination is necessary to prime an animal’s immune system against future attacks, so don’t even consider not vaccinating with the core vaccines,” Dr. Schultz says.

In 1997, the American Association of Feline Practitioners presented a recommended vaccination schedule for cats that has recently been updated. Dr. Schultz anticipates that a group of canine infectious disease experts will meet soon to endorse canine vaccination recommendations similar to the AAFP recommendations for cats. Recommendations from expert panels are very helpful in providing guidelines for veterinary practitioners and animal owners.

Still, Dr. Schultz feels that the ultimate decision on which vaccines need to be given and how often must be decided by the veterinarian and his/her client. There is no one vaccination program that is best for all animals, but there are a number of recommended schedules that can be followed depending on the needs and lifestyle of the pet. Many of these schedules and additional information on vaccines can be found in the following articles:

“Vaccination: Time to Take a Second Look,” Current and future canine and feline vaccination program by R.D. Schultz, in March 1998 issue of Veterinary Medicine

Recent Advances in Canine Infectious Diseases, Carmichael L.E. (Ed.); publisher: International Veterinary Information Service (www.ivis.org): “Considerations in Designing Effective and Safe Vaccination Programs for Dogs,” by R.D. Schultz, May 5, 2000.

Smith, C.A.: Current concepts - Are we vaccinating too much? JAVMA 207(4):421-425, 1995.

Feline Vaccination Guidelines, available from the American Association of Feline Practitioners, 6808 Academy Parkway E, Northeast, Suite B1, Albuquerque, NM 87109.