Feline Immunodeficiency Virus vaccine (Fel-O-Vax), is an inactivated vaccine (adjuvanted whole virus) produced by Fort Dodge Animal Health and was licensed for use in Canada in 2005 (9). The virus is active against 2 strains of FIV (Petaluma subtype A and Shizuoka subtype D) (1). FIV is made up of 5 serotypes (A,B,C,D,E) where A and B are the most predominant strains in North America and type D is more prevalent in Asia (1). A dual-subtype vaccine was created in an effort to produce a vaccine that would be effective globally (12).



The vaccine was shown to efficacious in preventing viremia. When vaccinated cats were challenged with FIV, only 16% developed viremia whereas 90% of the challenged control (not vaccinated) cats developed viremia. Studies on the vaccine also showed it produced protective immunity for a minimum of one year. (7)


However, use of the vaccination is controversial since vaccination results in production of FIV antibodies, which are indistinguishable from FIV antibodies produced due to natural infection. Therefore once vaccination has occurred infection due to natural disease is non-diagnosable. Consequently, there is still a chance that a vaccinated cat can acquire the infection a definitive diagnosis of the disease is unattainable. Knowledge of infection is useful for the owner to help manage the disease and prevent spread to other cats (1).


Recommended dosage of the vaccine is for use in healthy cats 8 weeks or older. Three, 1 mL subcutaneous injection should be administered 2 to 3 weeks apart and revaccination should occur annually. (5)