Are You Over Vaccinating Your Dog?

An ambitious study might prove rabies vaccinations can be given far less frequently, reducing adverse reactions.

If anyone had told Kris Christine 10 years ago that she would spearhead one of the most important scientific research projects ever to impact canine health, the suggestion would have been met with disbelief. The Alna, Maine, resident was not a veterinarian or a scientist. She was simply a dog lover — a noble pastime, but hardly one that immersed her in the world of cutting-edge canine research.

That all changed in the fall of 2003, however, when her then 6-year-old yellow Labrador Retriever, Meadow, received his rabies vaccine. Although the vaccine was labeled as a three-year inoculation, Maine law required that dogs receive the rabies booster every two years. Christine, a former personal assistant to Maine’s attorney general, complied — with tragic results. Shortly after receiving his rabies booster, Meadow developed an aggressive mast cell tumor at the injection site. Although the veterinarian couldn’t say definitively that the vaccine caused the tumor, the syringe puncture from Meadow’s rabies vaccination was visible in the center of the tumor.

Taking action

As Christine watched the cancer spread throughout Meadow’s body, she knew she had to take action to try to protect other dogs from unnecessary vaccinations, risking adverse reactions. In the U.S., public health authorities in each state — not the owner or the veterinarian — mandate how often dogs must receive rabies boosters. These laws are based in part on studies conducted in compliance with United States Department of Agriculture vaccine licensing guidelines.

In 2004, Christine successfully petitioned the state of Maine to change its rabies vaccination requirement to every three years. In 2005, she convinced them to add a medical exemption clause to the law, excusing ill dogs from rabies vaccination.

While poring over the research, Christine discovered a 1992 French study suggesting that the rabies vaccine provided immunity in dogs for five years — four years longer than the one-year vaccines and two years longer than the three-year licensed vaccines marketed in the United States. Because it was a French study, however, it’s not recognized in the United States.

Rabies is the only vaccine for which the USDA requires a minimum duration of immunity study. Every rabies vaccine on the market must undergo such a study showing that it provides immunity for a specific period of time. “I knew that if we hoped to change the laws, we needed to conduct a study that met these USDA criteria,” Christine says.

Spearheading new research

To facilitate such a study, Christine turned to two vaccine researchers — W. Jean Dodds, D.V.M., of Hemopet Animal Blood Bank in Garden Grove, Calif., and Ronald Schultz, Ph.D., professor and chair of the department of pathobiological sciences at the University of Wisconsin School of Veterinary Medicine in Madison.

Dodds and Schultz volunteered their time and expertise to design and complete the study. Christine registered the newly formed entity, the Rabies Challenge Fund, as a 501(c)3 charitable organization, and in November 2007, the fund ( launched with the purpose of studying the duration of immunity conveyed by the rabies vaccine.

The irony regarding minimum duration of immunity studies, according to Schultz, is that most one-year and three-year rabies vaccines are identical: the only difference is the product label. A few contain slightly different ingredients, but companies are reluctant to provide this information. Unlike human vaccines, veterinary vaccine components are proprietary. But the efficacy and duration of immunity are the same.

“A product labeled as a one-year rabies vaccine must be administered annually by law, even if it’s identical to the three-year vaccine,” Schultz says.

Schultz and his colleagues at the Rabies Challenge Fund have successfully managed to convince every state to adopt a three-year rabies vaccination policy. He notes that all dog owners should check their local regulations, however, since municipalities in some states have the right to set rabies laws that are stricter — but not more lenient — than state policies.

But Christine believes that decreasing rabies vaccine frequency from annually to every three years is not good enough. “Vaccines are not benign substances,” Christine says. “They are potent biologic drugs, and no dog should be unnecessarily exposed to them.”

Adverse reactions

Underreporting vaccine reactions in pets is a significant problem, and the adverse reports are generally those reactions seen within a few days of vaccination, not the longer-term adverse effects.

According to an article published in the Journal of the American Veterinary Medical Association (Frana, Clough, Gatewood, Rupprecht. Postmarketing surveillance of rabies vaccines for dogs to evaluate safety and efficacy. 2008; 232, 7), the USDA Center for Veterinary Biologics “received 246 adverse event reports for dogs in which a rabies vaccine was identified as one of the products administered” between April 1, 2004, and March 31, 2007.

Of those reports, the CVB categorized 217 as possibly related to at least one of the vaccines administered. The reactions reported included vomiting, facial swelling, injection site swelling or lump, lethargy, urticaria (hives), hair loss, autoimmune disorders, and death. About 72 percent of these dogs had received other vaccines or drugs in addition to the rabies vaccine, so it was not possible to definitively know if the rabies vaccine was the culprit.

The CVB also asked rabies vaccine manufacturers to submit their own adverse event report summaries. During the three-year period reviewed in the report, there were approximately 10,000 adverse event reports for all animals. About 65 percent of the reports involved dogs.

“Rabies vaccines are the most common group of biological products identified in adverse event reports received by the CVB,” the report states.

“Rabies vaccines are not more dangerous, but they do cause more adverse reactions in dogs because they are killed, adjuvanted products,” Schultz says.

Adjuvanted vaccines include substances called adjuvants that are specifically intended to enhance the immune response to killed, inactivated vaccines. More adverse reactions can occur with adjuvanted vaccines because the immune stimulants are often highly reactive to tissues, which is their purpose. Canine distemper and parvovirus vaccines are live and nonadjuvanted, and cause fewer adverse reactions, according to Schultz.

Changing vaccine requirements

The Rabies Challenge Fund must follow strict USDA guidelines for its results to be considered valid. The most controversial guideline involves “challenging” the study dogs — infecting them with the rabies virus — to establish their immunity rather than using titer tests. A titer test is a simple blood test used to check the strength of a dog’s immune defense to rabies by measuring his serum antibody titers. “Although we have repeatedly explained to the USDA the efficacy of titer tests and implored them to allow us to use this method, they continue to deny it as a valid proof of immunity in canine rabies studies,” Schultz says.

In order to minimize the number of rabies vaccines dogs must receive, the Rabies Challenge Fund hopes to prove the hypothesis that vaccinated dogs remain immune to rabies for five or seven years. “The dogs in the French study retained immunity five years after vaccination, so I believe we will have success,” Schultz says. “But although scientists have feelings, they must base their findings on the research results.”

Funding and lobbying for change

“There’s no financial incentive for vaccine manufacturers to pay for studies proving their products last longer than three years,” Christine says. She says it is the public, insisting on change, that is financing the study. “These are people who do not want to see innocent dogs suffer or die unnecessarily due to outdated vaccine protocols.”

Christine says that all the money donated, except for IRS fees and directors’ insurance, goes directly to fund the studies.

In addition to demonstrating that current rabies laws promote overvaccination of protected dogs, the Rabies Challenge Fund hopes to establish the efficacy of titer tests in measuring immunity so they can be used in lieu of rabies vaccines.

Schultz says that he receives a lot of inquiries from dog owners who want to titer their dogs for rabies instead of vaccinating them. “I have to tell them that there is no state in the U.S. that will allow titers in lieu of vaccination,” he says. “That’s something we’d like to change.”

The Rabies Challenge Fund would also like to change the public fear that surrounds rabies. “Right now, if a dog bites someone three weeks beyond the three-year vaccine period, that dog is considered nonvaccinated and a threat to public health,” Christine says. “That’s absurd, because a dog’s immunity to disease does not drop to zero three weeks beyond the three-year vaccine period any more than a human’s immunity to tetanus vanishes three weeks after he is due for a tetanus booster.”

The ultimate goal is to prove that the rabies vaccine protects dogs for at least seven years. “Establishing proof of seven years’ duration of immunity will give a lot of confidence from a public health standpoint that a dog who has received a couple of doses of vaccine will not be a threat again for his entire life,” Schultz says.

He concedes, however, that such proof might be met by resistance from many of his own colleagues. “Vaccination programs get dogs in the door, but the annual vet visit should focus on wellness exams rather than just vaccines,” he says. New findings might be slow to change laws, however, considering the number of years it took for every state in the U.S. to adopt three-year rabies revaccination intervals. In some of those states, individual cities and counties still have more restrictive laws (e.g., yearly or biennial revaccination laws).

Law versus science

Christine’s relentless campaign is about honoring the memory of Meadow and the dogs that came before him. “I have been blessed all of my life to care for amazing dogs who loved my family unconditionally,” she says. “Dogs contribute so much to our lives. This is a very small way that I can repay them for what they have given me.”

Schultz takes a more scientific outlook. “Rabies is the only vaccine you’re legally required to give,” he says. He goes on to say that even if the challenge studies show that protection lasts for a given number of years, the revaccination interval will be determined by regulatory authorities, not scientists. “Hopefully, one day the law will catch up with the science,” he says.  

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