Should Indoor Cats Receive the FeLV Vaccine?
Feline leukemia virus (FeLV) is a contagious and potentially fatal virus that affects cats exclusively. It suppresses the immune system and can lead to severe illness, including anemia, infections, and certain types of cancers such as lymphoma. While the virus has become less common due to improved testing and vaccination, it remains a threat — particularly for at-risk feline populations.
What Is FeLV and How Is It Transmitted?
FeLV is transmitted through exchange of bodily fluids, particularly saliva, and most commonly occurs in social interactions such as mutual grooming, biting, or via shared food and water bowls. It can also be passed from an infected mother to her kittens during pregnancy or nursing. Importantly, prolonged close contact is typically required for successful transmission.
Symptoms and Complications of FeLV
Cats infected with FeLV may not show immediate symptoms, but over time their health deteriorates. Common signs include:
- Pale gums (indicative of anemia)
- Loss of appetite and weight loss
- Recurring infections (e.g., respiratory, eye, skin, and urinary tract)
- Chronic diarrhea
- Fever and lethargy
- Enlarged lymph nodes
- Poor coat condition
Diagnostic Testing
Cats suspected of having FeLV can be tested using blood tests, most notably the ELISA test. While false positives are rare, veterinarians may recommend repeat testing, especially for kittens or ambiguous results. In early infection stages, some cats may clear the virus naturally. However, if the virus reaches the bone marrow, the infection persists for life.
The Role of Vaccination
Vaccination remains the most effective measure for preventing FeLV infection. The standard vaccination protocol includes:
- Initial series administered to all kittens starting at 8–12 weeks of age
- A booster dose administered 3–4 weeks later
For adult cats, FeLV vaccination is considered non-core. It is recommended for cats that go outdoors, live in multi-cat environments, or are exposed to cats of unknown FeLV status.
Is the FeLV Vaccine Necessary for Indoor Cats?
For indoor-only adult cats with no exposure to FeLV-positive cats, the vaccine is generally not necessary. Since extended close contact is needed for transmission, the risk to cats that live exclusively indoors is minimal — assuming no new, untested cats are introduced into their environment. In such low-risk scenarios, veterinarians may advise forgoing annual FeLV boosters after the initial kitten series.
Vaccine Efficacy and Safety
FeLV vaccines are highly effective, with some offering over 85% protection against persistent infection. Innovations like RNA-particle vaccines also provide at least two years of immunity after the initial two-dose series.
Side effects are generally mild and short-lived, such as temporary soreness, lethargy, or mild fever. In rare cases, a vaccination may be linked to injection-site sarcoma, a form of cancer, although such complications are uncommon and the benefit often outweighs the risk for at-risk cats.
Recommendations for Cat Owners
- Vaccinate all kittens as part of their core regimen
- Consider FeLV vaccination for any adult cat with potential exposure
- Test any new or unknown-status cat before introducing it to your household
- Consult your veterinarian for a personalized vaccination plan
Conclusion
FeLV remains a significant health risk for certain cats, especially those with outdoor access or multi-cat living situations. However, for indoor-only adult cats with no exposure to potentially infected animals, FeLV vaccination is usually not required after the kitten series. Pet owners should work with their veterinarians to assess risk and determine the best preventive strategy for their furry companions.
