Annual vaccinations come under scrutiny

Are changes in the wind?


For generations of pets, the annual booster vaccination has become a ritual - Fido goes to the clinic to get his inoculations and an exam that is considered a byproduct of the "shot visit" by many owners.

These days, for convenience and budgets, some owners forego the exam and take Fido or Fluffy to a pet supply store or a low-cost clinic for a jab of protection against rabies, distemper, parvovirus, and other canine diseases.

But change is in the wind. Research shows that vaccines have a longer term of effectiveness against disease than previously thought, and some veterinary colleges have published alternative vaccination protocols that suggest three-year intervals after the initial shots and a 12-month booster.

Some veterinarians go further; they divide vaccinations into two groups according to the prevalence of the disease in their area and recommend skipping vaccinations altogether for older animals that seldom leave home and for pets with already-compromised immune systems.

The changes may be a welcome, but they can have hidden dangers if pet owners forego the annual exam as a result. Fido needs that checkup even if he is fully protected against disease by last year's vaccination.

Why the switch?

An increase in knowledge about the canine immune system and more information about the length of time that immunity is conferred by particular vaccines have prompted veterinarians and researchers to question the yearly booster for adult dogs.

As a result, several universities have changed their vaccination recommendations and both the American Veterinary Medical Association and the American Animal Hospital Association have published changes in their vaccination guidelines.

"We are making this change after years of concern about the lack of scientific evidence to support the current practice of annual vaccination and the increasing documentation that over-vaccinating has been associated with harmful side effects," said the announcement of a new vaccination protocol at the Colorado State University Veterinary Teaching Hospital. "Boosters, the annual re-vaccination recommendation on the vaccine label is just that - a recommendation - and is not a legal requirement except for rabies. This recommendation could just as well have been every leap year or full moon and is not, in most cases, based on duration of immunity studies."

According to the AVMA policy statement approved in 2001, the annual revaccination recommendation found on many vaccine labels is based on historical precedent and US Department of Agriculture regulation, not on scientific data, and in cases where data has been provided, there are still questions about the duration of immunity provided by the injection.

Furthermore, there is evidence that some vaccines provide immunity for more than one year and that annual boosters may subject the dog to events such as suppression of the immune system, development of autoimmune disorders, or vaccine-site infections.

The AAHA recommendations approved in 2003 echo the same concerns about too-frequent vaccination and encourage owners to work with their veterinarians to devise a health program that takes into account the diseases that are a problem in the pet's environment.

So why vaccinate?

Although there is a growing concern over vaccine frequency, there is no doubt that vaccines control diseases that can kill puppies and dogs and protect individual dogs from illness and death.

According to an article in the Journal of the American Veterinary Medical Association in 1995, concerns about too-frequent vaccination center on the potential for vaccines to trigger autoimmune diseases in susceptible dogs. Data is scant, but suspicion is growing, according to Dr. Ronald D. Schultz of the University of Wisconsin Department of Pathobiological Sciences.

"I am a strong advocate of vaccine use," Dr. Schultz said in the JAVMA article. "We need to strike a balance between those who feel that no vaccines should be given and those who are vaccinating every week. Annual vaccination has become a knee-jerk response that, for the most part, is unnecessary. We have come a long way in reducing disease through vaccination, but perhaps we have gone too far."

How vaccines work

Vaccines stimulate the immune system to produce antibodies to the disease so that the dog is protected against various organisms in the environment. If the immunized dog is later exposed to the infectious agent, the antibodies react quickly to attack and destroy the disease. (See "Vaccination: Shield against canine diseases" at

Initial shots are given to puppies to gradually phase-in immunity as the mother's milk protection wears off. Puppies are generally vaccinated against parvovirus, distemper, adenovirus (vaccine also protects against hepatitis), and parainfluenza in combined shots and against rabies in a single vaccination given at the age of three months. They may be inoculated against leptospirosis, Lyme disease, and corona virus if local conditions warrant or if the pet will be traveling in an area where these diseases are known to be a problem. (See "Puppy viruses: Distemper and Parvovirus can mean big trouble" at

Vaccines come in two types: killed virus or bacterin and modified live virus or bacterin. The killed vaccines are mixed with an adjuvant to boost the effectiveness, and various adjuvants are suspected of causing problems. Killed vaccines are more stable, but they require more injections to immunize the pet and are more likely to cause allergic reactions ranging from low-grade fever or muscle aches to hives, facial swelling, or even vomiting and diarrhea. In rare cases, a pet may collapse within a few minutes of the injection from a severe anaphylactic reaction, but most reactions take a day or more to manifest.

Modified live vaccines work more quickly and for longer periods, are less expensive, and require only a single dose to be effective. However, they should not be used in sick animals and may cause suppression of the immune system in susceptible animals or abortions in pregnant bitches.

Vaccinations challenge the immune system in a complex manner, so it is not advisable to vaccinate a puppy or dog that is sick. Vaccines can fail if the animal has a fever or is taking steroids, or if they are given too close together or too far apart. They can also fail if the vaccine has been improperly handled or stored and may not protect a puppy that has lost immunity from mother's milk before the vaccine is administered.

Despite problems, vaccinations are still a pet owner's best line of defense against distemper and parvovirus that can kill puppies and young dogs, against rabies that will kill dogs - and people - of any age, and against other contagious diseases that can cause short term and long term health problems.

Pet owners should work with their veterinarians to design a vaccination schedule for each pet based on age, health status, reproductive status, and environment.

Rotating vaccines so that they are not all given at once is one option, and titer tests for antibodies is another. However, titer tests are more expensive than vaccinations and not completely reliable, so many vets do not recommend them.

Adverse reactions to vaccines should be reported to the veterinarian and the US Pharmacopeia, a private organization that operates a reporting program in conjunction with the American Veterinary Medical Association. USP can be reached at on the world wide web or at (800) 822-8772.

If veterinarians follow new protocols for vaccination intervals or owners and their veterinarians decide that particular pets don't need or should not receive annual vaccinations, the veterinarian should provide a statement to show at grooming shops, boarding kennels, or training schools. Those who plan to board pets or to take them to dog shows, dog parks, or other gatherings should add Bordatella vaccine to their inoculation protocol to protect against kennel cough. (See "Canine coughs: A cough is not necessarily a cold" at Initial Bordatella vaccine is administered through the nose; subsequent doses and boosters can be given as an injection.

Core and non-core vaccination

AAHA and AVMA suggest two vaccination programs for their clients: a core vaccine protocol for triennial vaccination against the high-risk, contagious, and potentially fatal diseases of rabies, parvovirus, adenovirus-2 (hepatitis vaccine), and distemper and a non-core schedule for protection against additional diseases that may be extant in particular regions of the country.

The AVMA describes a non-core vaccine program as follows:

"Non-core vaccines are those that target diseases that are of limited risk in the region, and/or represent less severe threats to infected patients, and/or vaccine benefit: risk ratios are too low to warrant the use of these products in all circumstances, and/or scientific information is inadequate to evaluate these products. Veterinarians and owners/clients need to carefully consider the benefits and risks of using these vaccine products on an individual basis."

Annual exams

"Annual boosters" for Fido and Fluffy is really shorthand for "yearly checkup."

The veterinarian does far more than inject the vaccine; he listens to heart and lungs, probes the belly, looks at teeth and gums, examines eyes and ears, checks for parasites and skin disorders, asks questions, watches the dog move. He discusses ideal weight and exercise if necessary, and listens to questions and concerns of the owner. Dogs that visit the veterinarian once a year live longer and are less likely to be surrendered to a shelter because the owner has an animal health professional to answer questions and to find potential problems before they become serious. Shot clinics in pet supply stores or elsewhere do not provide these opportunities.

Homeopathic remedies - an alternative to vaccines?

Herbal and homeopathic remedies and treatments such as acupuncture and chiropractic are gaining popularity as alternatives to modern medicine for people and pets, but it is highly unlikely that anything in this assortment of

alternative remedies will replace vaccinations against canine and feline diseases. Homeopathic nosodes have been used as a vaccine substitute and credited with preventing these diseases, but there are no studies that support their use on a broad scale and no quality assurance in their production.

Susan Gayle Wynn, DVM, said on the Alternative Veterinary Medicine website ( that ". . . unfortunately, there is no convincing evidence that nosodes do prevent disease. A few studies published in homeopathic journals suggest that nosodes may decrease the severity of active disease and possibly prevent the spread of epidemics, but these studies are not well-controlled."

Wynn, a homeopathic veterinarian, continued: "The results of one well-controlled study suggest that parvovirus nosodes are completely ineffective in preventing parvoviral disease under experimental challenge conditions. Until well-designed studies are completed and thousands of pet owners make a concerted effort to help with potential retrospective studies, nosodes remain an unknown quantity and I do not recommend using them as a sole strategy for disease prevention."

Dr. Wynn recommends puppy and kitten vaccinations followed by annual boosters for a year or two.


Homeopathic nosodes have been touted as alternatives to vaccinations. Homeopathy was developed in the late 1700s by German physician Samuel Hahnemann, who proposed that small doses of a substance could prevent or cure diseases caused by large doses of the same substance. This is the same principle behind the development of vaccines. Nosodes are produced according to Hahnemann's "law of infinitesimals," a technique that dilutes the original substance beyond recognition, leaving no recognizable traces of the original substance and no measurable protection in the animal's body. (See: "Homeopathic medicine: Herbalists, homeopaths gain ground in canine medicine" at

For more information

AAHA wraps up canine vaccine guidelines, DVM News Magazine,

Report of the American Animal Hospital Association Canine Vaccine Task Force: 2003 Canine Vaccine Guidelines, Recommendations, and Supporting Literature,

AVMA Policy & Guidelines - Principles of Vaccination ,

[Dog Owner's Guide: Vaccination: Shield against canine diseases]

Norma Bennett Woolf

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