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  Rabies is a deadly disease caused by a virus that attacks the nervous system of mammals. Spread through the saliva of an infected animal, the disease usually is fatal, say experts with the American Veterinary Medical Association (AVMA). Fortunately, vaccinating against rabies almost always prevents the disease. But vaccinating isn't without risk. So it's important to consider the benefits and drawbacks before deciding whether to vaccinate your cat.
  
  

How Vaccines Work

• Vaccines work by introducing antigens into the body that resemble a disease-causing organism, such as the rabies-causing virus. Ideally, if the body is exposed to the organism later, the immune system already will have prepared a response and be ready to successfully fight off the infection.
  
  

Reasons to Vaccinate

• Because so many people choose not to vaccinate, rabies in cats is on the rise, according to the AVMA. Reported infections in cats in the United States now far exceed the number in other domestic animals, making feline rabies a major public health concern. In most states, vaccination for rabies is required by law. After the initial vaccination and booster, subsequent boosters usually don't have to be repeated more frequently than every three years, unless local laws state otherwise.
  
  

The Risks

• Most vaccinations are administered without side effects. However, a risk-free vaccine doesn't exist, and there is a small chance your cat will develop a reaction. Still, the risk of reaction is far smaller than the risk of having your unvaccinated cat contract the deadly rabies virus, say experts with the American Association of Feline Practitioners.
  
  To minimize the risk, inform your veterinarian--before the procedure--of any past reactions your cat has had to vaccinations, any problems your cat is experiencing or any medication your cat is receiving.
  
  Mild reactions can start within a few hours of the vaccination or up to a week later. They may include discomfort at the site where the vaccine was given, mild fever, diminished appetite and activity, and sneezing. Your cat could develop a small, firm swelling under the skin where the vaccine was given. It's usually not painful and often disappears on its own.
  
  Very rarely, a cat may experience a serious and potentially life-threatening allergic reaction up to an hour after the vaccination. Called anaphylactic shock, the reaction often can be reversed with immediate veterinary care. The slowest reaction to appear can be a tumor, called a sarcoma, which may develop at the vaccine site up to several months later.
  
  If your cat experiences any reactions, notify your veterinarian immediately.