Feline Leukemia Vaccine (FeLV) for Cats: A Review by Emily Swiniarski, DVM, Revised by Catherine Barnette, DVM on June 30, 2025. Originally Published on June 26, 2020.

Feline Leukemia Vaccine (FeLV) for Cats: A Review by Emily Swiniarski, DVM, Revised by Catherine Barnette, DVM on June 30, 2025. Originally Published on June 26, 2020.

The Feline Leukemia Virus (FeLV) is a significant threat to the health of cats worldwide. To combat this virus, a vaccine was developed and introduced to the market in 1985 by veterinary scientists [1]. This article aims to provide a clear and concise overview of the FeLV vaccine, its purpose, and the factors that determine whether a cat needs it.

The FeLV vaccine has been approved by the United States Department of Agriculture (USDA) and is designed to protect cats against the symptoms of the feline leukemia virus [1]. Cats receiving the vaccine for the first time will receive two doses, administered 2-4 weeks apart [2]. However, it's important to note that if a cat tests positive for FeLV, it is not recommended to vaccinate against it [1].

The decision to vaccinate a cat against FeLV is largely dependent on several factors. Age plays a crucial role, with young cats under 1 year old, especially kittens, being considered for core vaccination [1]. The risk of exposure is another significant factor. Cats living in regions where FeLV infection is common or those with ongoing risk of exposure, such as outdoor cats, multi-cat households, or cats that have contact with unknown cats, are recommended to receive the vaccine [1][2][3].

Lifestyle and environment also play a role. Indoor cats with no contact with other cats generally have a lower risk and may not require the vaccine, whereas outdoor cats, breed cats, or those regularly rescued and introduced to new cats are at higher risk and should be vaccinated [2][3]. It's essential to consult with a veterinarian when making this decision, as they can weigh the specific risks and benefits based on the cat's circumstances [3].

It's worth mentioning that the FeLV vaccine comes in two different forms: inactivated virus vaccine and recombinant canarypox vector vaccine [1]. After vaccination, a cat's immune system creates a memory for a specific virus, providing immunity for at least a year in most cases [4]. While the vaccine may prevent the symptoms of FeLV disease, it does not necessarily prevent infection [5].

Before any cat is vaccinated against FeLV, they need to be tested for the virus to ensure they are not already infected [5]. The FeLV vaccine has been instrumental in reducing the impact of this deadly virus, despite the potential rare vaccine side effects [1][3].

In summary, the FeLV vaccine is essential for young cats with potential exposure and for cats living in high-risk environments, while cats with minimal exposure risk may not need it. By understanding the factors that determine the need for the FeLV vaccine and the benefits it provides, cat owners can make informed decisions to protect their feline friends from this potentially devastating virus.

References: [1] Merck Manual Professional Veterinary Edition. (2020). Feline Leukemia Virus Infection. https://www.merckvetmanual.com/cat-small-mammal/feline-diseases-and-disorders/feline-leukemia-virus-infection [2] American Association of Feline Practitioners. (2021). Feline Leukemia Virus (FeLV) Vaccination Guidelines. https://www.catvets.com/assets/1/16/Feline_Leukemia_Vaccination_Guidelines.pdf [3] Cornell University College of Veterinary Medicine. (2021). Feline Leukemia Virus (FeLV). https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-leukemia-virus-fellv [4] American Veterinary Medical Association. (2019). Vaccine Duration of Immunity. https://www.avma.org/resources/pet-owners/petcare/vaccine-duration-immunity [5] American Association of Feline Practitioners. (2021). Feline Leukemia Virus (FeLV) Vaccination FAQs. https://www.catvets.com/assets/1/16/Feline_Leukemia_Vaccination_FAQs.pdf

1. Science plays a crucial role in combating medical conditions like the Feline Leukemia Virus (FeLV), as demonstrated by the development of a vaccine in 1985.
2. In the workplace-wellness sector, understanding chronic diseases such as FeLV is essential to ensure animal health and safety.
3. Chronic-kidney-disease and COPD are examples of human chronic diseases, but FeLV is significant in the feline world.
4. Type-2-diabetes and cancer are also human health issues, while FeLV presents similar challenges for cats.
5. Respiratory-conditions like asthma in humans and FeLV in cats share the need for proper management and treatment.
6. Digestive-health is important for both humans and cats, but FeLV can affect the cat's immune system, making them more susceptible to other diseases.
7. Eye-health can be affected by FeLV in cats, negatively impacting their overall well-being.
8. Hearing loss is a concern for both humans and animals, but FeLV in cats weakens their immune system, making them more vulnerable to other health issues.
9. Health-and-wellness is a broad field encompassing human and animal diseases, including FeLV in cats.
10. Fitness-and-exercise is crucial for maintaining overall health and can help manage symptoms in humans with chronic diseases like diabetes and in cats with FeLV.
11. Alzheimer's disease is a neurological disorder affecting humans, while multiple-sclerosis and migraines also fall under the umbrella of neurological disorders.
12. Autoimmune-disorders like rheumatoid-arthritis are human health concerns, but can also be found in cats with FeLV.
13. Climate-change affects the environment and can exacerbate health issues, including the spread of diseases like FeLV.
14. Renewable-energy sources offer a sustainable solution to reduce the impact of climate change on health and the environment.
15. In the manufacturing industry, workers must protect themselves from harmful chemicals and maintain their mental-health for optimal workplace wellness.
16. Skin-care products and therapies are essential for addressing conditions like psoriasis, not only in humans but also in cats with skin problems due to FeLV.
17. Nutrition plays a vital role in managing weight-management and other health issues, such as FeLV in cats.
18. Mental-health is crucial for both humans and animals, and cats with FeLV may experience emotional changes due to their illness.
19. In addition to FeLV, skin-conditions like dermatitis can affect the health of cats.
20. Therapies-and-treatments for various diseases, including FeLV in cats, are continually evolving and improving due to advancements in the field of medical-conditions.
21. CBD products have been used to manage pain and anxiety in humans, but more research is needed to determine their effectiveness for treating symptoms in cats with FeLV.
22. Rheumatoid-arthritis and other autoimmune-disorders can cause physical discomfort and mobility issues in humans.
23. Neurological-disorders like Alzheimer's disease and multiple-sclerosis can lead to cognitive decline and mobility issues in humans.
24. Breast-cancer is a significant health concern for women, while FeLV poses a threat to cats.
25. Environmental-science plays a role in understanding the factors that contribute to the spread of diseases like FeLV and how to mitigate their impact.
26. Financial institutions, such as banks and insurance companies, play a role in the health industry by providing coverage and assistance for various medical-conditions, including FeLV in cats.

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