For Some Pet Diseases, Yearly Boosters Are Based On Tradition, Not Science
By Rhonda L. Rundle
The Wall Street Journal
(Copyright (c) 2002, Dow Jones & Company, Inc.)
AFTER RECEIVING a reminder in the mail from his veterinarian, Jim Schwartz took his 11-year-old poodle, Moolah, for her annual rabies shot. A few weeks later she fell ill and was diagnosed with an autoimmune disease. As her suffering worsened, Mr. Schwartz put her down.
There's no proof that the rabies shot killed Moolah and Mr. Schwartz didn't immediately suspect any link. But when the retired financial planner learned that some veterinarians are vaccinating pets less frequently because of possible fatal side effects, he was furious. "No dog should have to go through what Moolah did," he says.
Evidence is building that annual vaccination of dogs and cats -- performed for diseases such as rabies, distemper and parvovirus -- may not be necessary and could even be harmful. Vaccines licensed by the U.S. Department of Agriculture are tested to ensure they protect pets against disease, usually for one year. But the tests don't detect long-term side effects, or measure the duration of a vaccine's effectiveness. Recent and continuing studies at several universities suggest that protection from vaccines may last for years, which would make annual shots for some diseases a waste of money -- at the very least.
Fears of vaccine-induced diseases date back more than 40 years. But a sharp increase during the past decade in cancerous tumors among cats, between the shoulder blades where vaccines typically are injected, has spurred studies. Some have found a higher-than-expected incidence of side effects. "We see health problems in dogs for which we have no explanation. The classic one is autoimmune disease," says Larry Glickman, professor of epidemiology at Purdue University's School of Veterinary Medicine in West Lafayette, Ind., who is studying possible links with vaccinations. "We see an epidemic of hyperthyroidism in cats today, and we suspect that these are happening because we're over-vaccinating our pets."
Dr. Glickman and his colleagues theorize that repeated vaccination causes dogs to produce antibodies against their own tissue. The antibodies are caused by contaminants in the vaccine introduced in the manufacturing process. While the amounts are minuscule, they gradually accumulate with repeated vaccinations over the years. But Dr. Glickman cautions that more research is needed before a clear link can be established between antibody levels and autoimmune disease.
Vaccination recommendations for cats and dogs vary around the country. Most states require rabies vaccinations every three years, while a handful of states -- as well as some individual cities and counties -- have mandated annual shots due to local problems with rabies in wild animals. Some other vaccinations are given only when a pet's lifestyle or environment exposes it to a particular risk, such as Lyme disease.
Pet diseases other than rabies aren't a threat to people, thus vaccinations aren't required by law. But veterinarians and vaccine makers have traditionally recommended annual booster shots against potentially fatal diseases such as distemper and parvovirus in dogs and herpesvirus in cats. In a policy statement last year, the American Veterinary Medical Association acknowledged that the practice of annual vaccinations is based on "historical precedent" and "not on scientific data."
The emerging evidence of health risks is prompting some vets to change their practices. "We're now doing 40% less vaccinations than five years ago," says Kathleen Neuhoff, a veterinarian in Mishawaka, Ind., and president of the American Animal Hospital Association, Lakewood, Colo.
"My own pets are vaccinated once or twice as pups and kittens, then never again except for rabies," Ronald D. Schultz, chairman of the University of Wisconsin's Department of Pathobiological Sciences, wrote in the March 1998 issue of Veterinary Medicine.
Some critics of annual shots accuse some vets of ignoring research about vaccine risks for financial reasons. "Vets are afraid they will go broke" without regular vaccines, which account for about 20% of their practice income, says Bob Rogers, a Spring, Texas, veterinarian and outspoken critic of current practices.
Other vets deny that financial motives are involved. ("No one who is motivated by money would ever become a veterinarian," Dr. Neuhoff says.) "The concern is that if we move too quickly to decrease vaccine frequency across the board, we may be opening the door for some animals to become infected when we could have prevented the problem," says Todd R. Tams, chief medical officer of VCA Antech Inc., in Los Angeles, the nation's largest owner of veterinary hospitals.
No one truly knows how long protection from vaccines lasts. Vaccine makers say that proving their duration would be expensive and would require large numbers of animals to be isolated for years.
One company, Pfizer Inc., decided to test its one-year rabies vaccine on live animals and discovered it lasted for at least three years. It sells the identical formula simply packaged under different labels -- Defensor 1 and Defensor 3 -- to satisfy different state vaccination requirements.
(See related article: "Testing Animals' Immunity Level" -- WSJ July 31, 2002)