The immune system plays a pivotal role in maintaining your cat's health. One of the most important functions of this highly complex system of specialized cells and molecules is to protect cats from disease and infection caused by foreign invaders - viruses, bacteria, and a host of other microbes and parasites intent on assaulting the body and causing disease.

Vaccines are given to prepare the body's immune system against invasion by a particular disease-causing organism. Vaccines contain antigens which to the immune system "look" like the organism but don't, ideally, cause disease. When the vaccine is introduced by injection or some other means, the immune system responds by mounting a protective response. When the cat is subsequently exposed to the organism, the immune system is prepared and either prevents infection or reduces the severity of disease.

No. The choice of which vaccines your cat should receive is dependent on a number of factors including:

• 1) Your cat's risk of exposure to the disease-causing organism (in part dependent on the health of other cats to which yours is exposed, and the environment in which your cat lives)
• 2) The consequence of infection
• 3) The risk an infected cat poses to human health (e. g., rabies)
• 4) The protective ability of the vaccine
• 5) The frequency or severity of reactions the vaccine produces
• 6) The age and health status of your cat
• 7) Vaccine reactions your cat may have experienced in the past

Your veterinarian will help guide you in deciding which vaccines are appropriate for your cat. The following vaccines are currently available:

Feline panleukopenia (also called feline distemper) is a highly contagious and deadly viral disease of cats. Feline panleukopenia virus is extremely hardy, is able to survive extremes of temperature and humidity for many months, and is resistant to most available disinfectants. Until recent years, panleukopenia was the most serious infectious disease of cats, claiming the lives of thousands every year. Thanks to the highly effective vaccines currently available, panleukopenia is now considered to be an uncommon disease. However, because of the serious nature of the disease and the continued presence of virus in the environment, vaccination is highly recommended for all cats.

Feline calicivirus and feline herpes virus type I are responsible for up to 80-90% of all feline upper respiratory tract disease. Most cats are exposed to either or both of these viruses at some time in their lives. Once infected, many cats never completely rid themselves of virus. These "carrier" cats either continuously or intermittently shed the organisms for long periods of time -- perhaps for life -- and serve as a major source of infection to other cats. The currently available vaccines will minimize the severity of upper respiratory infections, although none will prevent disease in all situations. Vaccination is highly recommended for all cats.

Rabies is an increasing threat to cats. At the present time, the number of reported feline rabies cases in the United States far exceeds that of all other domestic animals. Rabies in cats is also a major public health concern. Because of the routinely fatal outcome of infection in cats, and the potential for human exposure, rabies vaccination is highly recommended for all cats; it is required by law in most areas of the country.

Feline leukemia virus (FeLV) is the leading viral killer of cats. The virus is spread from cat-to-cat through bite wounds, through casual contact with infected cats, and from an infected mother cat to her kittens. The individuals most at risk of infection are outdoor cats, indoor/outdoor cats, and cats exposed to such individuals. Cats living in households with FeLV-infected cats or with cats of unknown infection status are also at risk. Indoor-only cats with no exposure to potentially infected cats are extremely unlikely to become infected. FeLV vaccines are recommended for all cats at risk of exposure to the virus.

Vaccines are available for each of these disease-causing organisms, but their use is not routinely recommended for all cats. Your veterinarian will help guide you in deciding whether your cat should receive any of these vaccines.

Kittens receive antibody from colostrum (the first milk the mother produces) that is ingested during the early hours after birth. Maternal antibody helps protect against infectious disease until the kitten's own immune system is more mature. Unfortunately, maternal antibody also interferes with a vaccine's ability to stimulate the kitten's immune system. To counteract this problem, veterinarians often administer a series of vaccines, usually beginning when the kitten is around six to eight weeks of age, and then repeating vaccination at three or four week intervals until maternal antibody has waned, usually at around twelve weeks of age. In some cases (e.g., rabies) the initial vaccine is not given until maternal antibody has disappeared.

The answer depends upon the vaccine. Certain feline rabies vaccines provide protection for longer than one year, so vaccination with a triennial-approved rabies vaccine every three years (after the initial series is completed and when consistent with local rabies vaccine requirements) is sufficient. Recent research has provided compelling evidence to suggest that panleukopenia/rhinotracheitis/calicivirus vaccines provide adequate protection for several years, so in response, many veterinarians are now recommending that this vaccine be 'boosted' at three year intervals as well. Unfortunately, far less is known about the duration of protection provided by other vaccines. Until that information is known, annual vaccination with those products is a reasonable course of action.

Not usually. Unfortunately, a perfect, risk-free vaccine does not exist. Without question, vaccines have saved countless lives, and they continue to be indispensable weapons in the battle against feline infectious disease. But as with any medical procedure, there is a small chance that reactions may develop as a result of vaccination. In most cases, the risks associated with vaccination are much smaller that the risks of disease if vaccines were not given. But to minimize the risk, before your cat is vaccinated, please inform your veterinarian of any problems your cat is experiencing or any medication your cat is receiving.

Following is a brief list of reactions that may occur after vaccination. if your cat has had any reaction in the past as a result of vaccination, be sure to inform your veterinarian before your cat is vaccinated again.

The following reactions are fairly common, usually start within hours to several days after vaccination, and last no more than several days:

• discomfort at the site where the vaccine was given
• mild fever
• diminished appetite and activity
• sneezing at about four to seven days after administration of an intranasal vaccine

Development of a small, firm, non-painful swelling under the skin at the site where the vaccine was given. The swelling usually goes away after several weeks, but if you notice such a swelling, you should contact your veterinarian.

These reactions occur very rarely:

By all means, consult with your veterinarian. Even though vaccine-related disease is uncommon, the consequences can be serious. Your veterinarian is the individual most qualified to advise you if an untoward event does occur.

The decision to vaccinate your cat should be based on a thorough understanding of the benefits--and the risks-- of the procedure. For this reason, it is extremely important that you discuss the procedure with your veterinarian. He or she will be more than willing to answer any questions you may have, and will help you make the right vaccine choices for your cat.