Dear Doctor: Confusion about Feline Vaccines


Q I have three adopted cats, and we live in the country. They are all indoor cats. Recently, I learned that my neighbor has a bat problem in the attic of her old house. Of course, this got me thinking about the possible risk to my own pets.

Can you explain the difference between the yearly rabies vaccination and the one that is given once each three years?
Elizabeth Dozen-Smith

A Dear Elizabeth: There are three reasons why a rabies vaccination would only be good for one year: age at time of administration, vaccine licensing, and state regulations. Allow me to further elaborate.

In the United States, the recommendation is for kittens to receive their first rabies vaccination at the age of 12 weeks or older. This first vaccination is always good for 12 months, and never three years. It is believed the immune system is primed by this initial vaccination with a longer lasting response after the next. The second vaccination may be good for three years.

Some rabies vaccines are licensed for yearly administration. Others are licensed for every three year administration. Why ever choose a one-year vaccine? Some one year vaccines are less irritating, which may decrease the risk for injection-site reactions. For a cat that will only receive a one year vaccine regardless of which product is used, some veterinarians choose to use a one-year licensed vaccine.

State regulations may supersede any guidelines I’ve stated. For example, some states require yearly revaccination regardless of which vaccine is used. Massachusetts has an additional requirement that the second vaccination must be nine to 12 months after the first. If the patient is revaccinated one day before nine months, or one day after 12 months, that vaccine is only good for one year. A three-year rabies vaccine in Massachusetts can only be offered when two vaccinations are performed nine to 12 months apart.

I realize this is a bit confusing! Your veterinarian will take into consideration your pet’s age, the licensing of the vaccination itself and state regulations to help determine the most appropriate vaccine schedule for your pet.
Michael Stone DVM, DACVIM
Clinical Assistant Professor
Cummings School of Veterinary
Medicine at Tufts University


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