Debra Grierson leaves the veterinarian's office clutching Maddie and Beignet, her Yorkshire terriers, and a credit card receipt for nearly $400. 

That's the cost for the tiny dogs' annual exams, including heartworm checks, dental checks and a barrage of shots. 

"They're just like our children," said the Houston homemaker. "We would do anything, whatever they needed." 

What many pet owners don't know, researchers say, is that most yearly vaccines for dogs and cats are a waste of money -- and potentially deadly. Shots for the most important pet diseases last three to seven years, or longer, and annual shots put pets at greater risk of vaccine-related problems. 

The Texas Department of Health is holding public hearings to consider changing the yearly rabies shot requirement to once every three years. Thirty-three other states already have adopted a triennial rabies schedule. Texas A&M University's and most other veterinary schools now teach that most shots should be given every three years. 

"Veterinarians are charging customers $36 million a year for vaccinations that are not necessary," said Bob Rogers, a vet in Spring who adopted a reduced vaccine schedule. "Not only are these vaccines unnecessary, they're causing harm to pets." 

Just as humans don't need a measles shot every year, neither do dogs or cats need annual injections for illnesses such as parvo, distemper or kennel cough. Even rabies shots are effective for at least three years. 

The news has been slow to reach consumers, partly because few veterinarians outside academic settings are embracing the concept. Vaccine makers haven't done the studies needed to change vaccine labels. Vets, who charge $30 to $60 for yearly shots, are loath to defy vaccine label instructions and lose an important source of revenue. In addition, they worry their patients won't fare as well without yearly exams. 

"I know some vets feel threatened because they think, `People won't come back to my office if I don't have the vaccine as a carrot,' " said Alice Wolf, a professor of small-animal medicine at Texas A&M and an advocate of reduced vaccinations. "A yearly exam is very important." 

The movement to extend vaccine intervals is gaining ground because of growing evidence that vaccines themselves can trigger a fatal cancer in cats and a deadly blood disorder in dogs. 

Rogers conducts public seminars on the subject with evangelical zeal but thus far has been unsuccessful in persuading the Texas Veterinary Medical Association to adopt a formal policy. 

"I'm asking the Texas attorney general's office if this is theft by deception," said Rogers, whose Critter Fixer practice won an ethics award from the Better Business Bureau in 2000. "They just keep coming out with more vaccines that are unnecessary and don't work. Professors give seminars, and nobody comes and nobody changes." 

When rabies shots became common for pets in the 1950s, no one questioned the value of annual vaccination. Distemper, which kills 50 percent of victims, could be warded off with a shot. Parvovirus, which kills swiftly and gruesomely by causing a toxic proliferation of bacteria in the digestive system, was vanquished with a vaccine. Over the years, more and more shots were added to the schedule, preventing costly and potentially deadly disease in furry family members. 

Then animal doctors began noticing something ominous: rare instances of cancer in normal, healthy cats and an unusual immune reaction in dogs. The shots apparently caused feline fibrosarcoma, a grotesque tumor at the site of the shot, which is fatal if not discovered early and cut out completely. Dogs developed a vaccine-related disease in which the dog's body rejects its own blood. 

"That really caused people to ask the question, `If we can cause that kind of harm with a vaccine ... are we vaccinating too much?' " said Ronald Schultz, a veterinary immunologist at the University of Wisconsin School of Veterinary Medicine. "As you get more and more (vaccines), the possibility that a vaccine is going to cause an adverse event increases quite a bit." 

Less frequent vaccines could reduce that risk, Schultz reasoned. Having observed that humans got lifetime immunity from most of their childhood vaccines, Schultz applied the same logic to dogs. He vaccinated them for rabies, parvo, kennel cough and distemper and then exposed them to the disease-causing organisms after three, five and seven years. The animals remained healthy, validating his hunch. 

He continued his experiment by measuring antibody levels in the dogs' blood nine and 15 years after vaccination. He found the levels sufficient to prevent disease. 

Fredric Scott, professor emeritus at Cornell University College of Veterinary Medicine, obtained similar results comparing 15 vaccinated cats with 17 nonvaccinated cats. He found the cats' immunity lasted 7.5 years after vaccination. In 1998, the American Association of Feline Practitioners published guidelines based on Scott's work, recommending vaccines every three years. 

"The feeling of the AAFP is, cats that receive the vaccines every three years are as protected from those infections as they would be if they were vaccinated every year," said James Richards, director of the Feline Health Center at Cornell. "I'm one of many people who believe the evidence is really compelling." 

Texas A&M's Wolf said the three-year recommendation "is probably just as arbitrary as anything else," and nothing more than a "happy medium" between vaccine makers' recommendations and the findings by Schultz and Scott aimed at reducing vaccine-related problems. 

But many vets are uncomfortable making a drastic change in practice without data from large-scale studies to back them up. There is no animal equivalent of the U.S. Centers for Disease Control and Prevention, which monitors outbreaks of vaccine-preventable disease in people, thus keeping tabs on a vaccine's effectiveness. 

Federal authorities require vaccine makers to show only that a vaccine is effective for a reasonable amount of time, usually one year. Richards notes that studies to get a feline vaccine licensed in the first place are typically quite small, involving 25 to 30 cats at most. 

There is no federal requirement to show a vaccine's maximum duration of effectiveness. Arne Zislin, a veterinarian with Fort Dodge Animal Health, the largest animal vaccine maker in the world, said such studies would be expensive and possibly inhumane, requiring hundreds of animals, some of them kept in isolation for up to five years. 

"I don't think anyone with consideration for animals would really want to go through that process," said Zislin, another vet who believes current data are insufficient to support an extended schedule. 

Diane Wilkie, veterinarian at Rice Village Animal Hospital, said she tells pet owners that vaccines appear to last longer than a year, but her office hasn't officially changed its protocol yet. She said 20 percent to 30 percent of her cat patients are on the extended schedule. 

"It's kind of a hard situation. The manufacturers still recommend a year, but they're the manufacturers," Wilkie said. "It's hard to change a whole professional mentality -- although I do think it will change." 

In Houston, yearly pet examinations typically cost $50 to $135, with shots making up one-third to half of the expense. A dental check, heartworm test, fecal check and overall physical are usually included in the price. Without the shots, vets could expect to lose a chunk of that fee. 

But an increasing number of vets are emphasizing other services, such as surgery. Wolf said savings on vaccines might prompt pet owners to get their pets' teeth cleaned instead. An in-house test to check antibody levels is in development. 

"I definitely think there's a profit issue in there; don't get me wrong," Wilkie said. "(But) people are willing to spend money on their pets for diseases. Although vaccines are part of the profit, they aren't that big a part. We just did a $700 knee surgery." 

Vaccination findings 

Veterinary research challenges the notion that pets need to be vaccinated every 12 months. Some of the findings: 

Dog vaccines/Minimum duration of immunity
· Canine rabies3 years 
· Canine parainfluenza3 years 
· Canine distemper (Onderstepoort strain)5 years 
· Canine distemper (Rockborn strain)7 years 
· Canine adenovirus (kennel cough)7 years 
· Canine parvovirus7 years 

Cat vaccines/Minimum duration of immunity
· Cat rabies3 years 
· Feline panleukopenia virus6 years 
· Feline herpesvirus5 or 6 years 
· Feline calicivirus3 years 

Recommendations for dogs
· Parvovirus, adenovirus, parainfluenza, distemper: Following initial puppy shots, provide booster one year later, and every three years thereafter. 
· Rabies: At 16 weeks of age, thereafter as required by law. 
· Bordatella: Use prior to boarding; may be repeated up to six times a year. 
· Coronavirus: Not recommended in private homes. Prior to boarding, may be given to dogs 8 weeks or older, and repeated every six months. 
· Lyme: Not recommended. 
· Giardia: Not recommended. 

Recommendations for cats
· Panleukopenia, herpesvirus (rhinotracheitis), calicivirus: Following initial kitten shots, provide booster one year later and every three years thereafter. 
· Rabies: At 8 weeks of age, thereafter as required by law. 
· Feline leukemia: Use only in high-risk cats. Best protection is two vaccines prior to 12 weeks of age, with boosters repeated annually. 
· Bordatella: Use prior to boarding. 
· Feline infectious peritonitis: Not recommended. 
· Chlamydia: Not recommended. 
· Ringworm: May be used during an outbreak in a home. 

Sources: Ronald Schultz, University of Wisconsin School of Veterinary Medicine; Fredric Scott, Cornell University College of Veterinary Medicine; Colorado State 
University; University of California-Davis Center for Companion Animal Health.