Does My Cat Need To Be Vaccinated for Feline Leukemia?

Feline Leukemia Vaccination for Cats

Cats that are at risk for feline leukemia should be vaccinated. Others should not. Photo Credit: Magic Madzik/

Feline leukemia is a relatively common disease in cats. Unlike leukemia in people, feline leukemia is caused by a virus. The disease is contagious and is usually fatal once signs of disease appear. However, many cats test positive for the feline leukemia virus without showing signs of disease.

In the past, veterinarians recommended vaccinating all cats for feline leukemia because of the deadly nature of the disease. However, we now realize that vaccines are not innocuous and can cause unwanted side effects. As a result, modern vaccination protocols are tailored to fit the needs of the individual pet. Only cats at risk of infection with feline leukemia should be vaccinated against the disease.

Which Cats Are At Risk for Feline Leukemia Infection?

Though feline leukemia is considered to be a contagious disease, not all cats are at risk of contacting the disease. Spread of feline leukemia requires close contact with an infected cat. Casual contact is generally not sufficient to allow transmission of the virus.

Cats that socialize frequently with other cats are at highest risk of exposure to disease. This includes cats that live outdoors or spend significant amounts of time outdoors around other cats. Cats that live exclusively indoors and never contact other cats are at very little, if any, risk.

Which Cats Should Be Vaccinated Against Feline Leukemia?

Only those cats who are at risk of infection should be considered candidates for feline leukemia vaccination.

  • The feline leukemia vaccine has been implicated as a potential cause or at least a contributory factor in the development of an aggressive type of tumor known as a vaccination-induced sarcoma in a small but significant number of cats. We don’t understand exactly what causes this type of tumor or why some cats develop the tumor while others do not. However, the risk of sarcoma development together with the risk of other potential complications (such as allergic reactions) make it important to weigh the potential risks against the benefits of giving the vaccine.
  • Outdoor cats who socialize frequently with other cats are candidates for the vaccine. However, indoor cats who never contact any other cats should not be vaccinated.
  • Young cats are more susceptible to infection with feline leukemia. Older cats often develop a certain amount of natural immunity.
  • Some veterinarians do recommend routinely vaccinating kittens against feline leukemia. This is sometimes recommended because kittens are more susceptible to the virus than mature cats and often owners are uncertain whether the kitten will be allowed outdoors.

About Lorie Huston, DVM

Lorie Huston, DVM has written 88 posts in this blog.

Lorie Huston is a veterinarian with 20+ years of experience with dogs and cats. She is also a talented free-lance author and blogger and has contributed to numerous publications, including Pet Sitter's WORLD, FIDOFriendly, Dancing Dog Blog, Dawg Business and many others. Lorie is the featured pet care writer at, a contributing writer in Dog and Cat Diseases and Conditions at and the National Pet Health Examiner at In addition, she is a host of the popular podcast/review site, Animal Cafe.


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