Veterinarians question whether pets receive more vaccinations than necessary and say the consequences can cause serious harm.

Pet owners spent more than $28 billion on veterinary bills in one year, according to the latest statistics available through the American Veterinary Medical Association.  It also found that 84 percent of people vaccinated their dogs in that same year.

"I think we do vaccinate more than we should for some of those diseases," said veterinarian Dr. Brad Hines.

Hines is overseeing pet owner Beth Olkowski's bulldog's treatment. Olkowski's dog Molly was diagnosed with immune mediated hemolytic anemia, or IMHA.

Olkowski described Molly as a dog with a big personality.  A few months ago, she noticed Molly started to become lethargic. She also stopped eating and started vomiting.

The dog's liver had shut down. Olkowski took her to see a vet, then to an emergency room where she was diagnosed with IMHA.

"I had never heard of it," said Olkowski.

IMHA causes an animal's immune system to attack red blood cells. The odds of surviving the disease are often not good. Molly's prognosis was bleak.

"I wanted her to be OK.  I really needed her to be OK," said Olkowski.

Olkowski started researching the link between the autoimmune disease and vaccinations. She asked Hines about the association between the two.

"Do I think vaccinations may play (a) role in the development of the disease? Yes I do. The hard part is proving it," said Hines.

Hines said vaccinations are important and so is making sure not to over-vaccinate.

Pet owner Jim Schwartz believes his poodle Moolah died from an illness induced by a vaccination. Since then he has proposed legislation and written a book to raise awareness of the issue.

"I swore that what happened to Moolah need not, should not, happen to another dog," said Schwartz.

Dr.W Jean Dodds is a veterinarian based in Santa Monica. She is the founder of Hemopet and has spent years researching animal vaccinations.  She said there is a close association with vaccinations and certain illnesses.

"Certain families of dogs are getting it over and over again. It doesn't take a rocket scientist to hit you on the head to say, 'Wait a minute, there is an association here, it's unacceptable,'" said Dodds.

She wrote an article called "Changing Vaccine Protocol." The article points to research that found there were 38 adverse events for every 10,000 dogs vaccinated. It also said certain factors increased a dog's risk of adverse reactions, including multiple vaccines giving at the same time and small breeds.

Dr. Jeff Fankhauser spoke on behalf of the Colorado Veterinarian Medicine Association. He said vaccines are essential to keep pets healthy and the risks of not vaccinating animals are small compared to the consequences of not vaccinating them.

"The benefits of vaccinations certainly outweigh the risks, I have vaccinated tens of thousands of animals during my career and I have only seen a few dozen significant vaccine reactions," said Fankhauser.

While 60 percent of veterinary visits are for vaccinations, Fankhauser said the most essential part of that visit is the dog's physical examination.

"I don't look at vaccines as a reason to go to the vet per se," said Fankhauser.

Dodds said it doesn't make sense for small breeds receive the same size dosage of a vaccination as large breeds.

"When you look at public data from other countries, like the (Asian) or Scandinavian countries, they clearly show smaller doses for toy breeds work just as well , if not better," said Dodds.

Fankhauser disagreed and said size doesn't matter.

"You aren't dealing with a vaccination that's based on body weight, it's based on the immune system and animals' immune systems aren't necessarily different sizes so that's why it's important to look at it as one product regardless of the size," said Fankhauser.