Question: 

If I understand the guidelines correctly, you recommend starting vaccines as early as 4 weeks, and revaccinating as often as every 2 weeks until 20 weeks of age. That seems like a lot! Is there a maximum number of FVRCP vaccines a kitten should receive between 4-20 weeks?

Answer: 

It’s true that if a kitten is initially given an FVRCP vaccine at 4 weeks of age and gets re-vaccinated every 2-3 weeks, then they could receive up to 9 vaccines by 20 weeks of age. This schedule is recommended in a high risk environment such as a shelter or rescue with many transient cats passing through. Ideally kittens should not be held in that sort of environment for three months, and when in a lower risk environment (such as a home or clean foster situation), vaccines can be started at a later age and the frequency of revaccination can be reduced. However, there isn’t a maximum or specific number of vaccines kittens should receive to be protected, rather they should continue to receive vaccines until they are 18-20 weeks old.

Understanding the reason why we do a series of vaccinations in kittens (and puppies) until this age can help clarify this point.  Kittens receive a variable amount of maternal antibodies through colostrum that can provide protection against the viruses we are concerned about.  The problem however, is that these maternal antibodies can interfere with the ability to become immunized following vaccination. Maternal antibodies diminish over time and we know that they are typically absent in kittens by 18-20 weeks of age. For more in depth discussion see our Vaccination in Animal Shelters information sheet. The first vaccine that gets past these maternal antibodies will provide effective protection (whether that ends up being the first, second, third, etc. vaccine we give is unknown to us). For this reason, the actual number of vaccines is not as critical as ensuring kittens receive repeat vaccinations until the age of 20 weeks, which is when we know with most certainty that their maternal antibodies have diminished.

The American Association of Feline Practitioners publishes guidelines for feline vaccination, including shelter-specific protocols. Their recommendation for vaccination of shelter-housed kittens is to administer a modified-live subcutaneous FVRCP vaccination beginning at 4-6 weeks of age and repeating every 2-3 weeks until 16-20 weeks of age. For pet kittens in a home, where the risk of exposure to viruses such as panleukopenia is presumed to be lower than in a shelter, their recommendation is to start FVRCP vaccination as early as 6 weeks of age and then repeat every 3-4 weeks until 16-20 weeks of age. An earlier age of first vaccination and shorter inter-vaccination interval is recommended when the risk of infectious disease is high, e.g. shelter housing. Other higher-risk scenarios would be foster homes that are unable to effectively disinfect between litters or those with kittens from multiple sources. In these, we would advise revaccination every 2 weeks with the aim to reduce the window of susceptibility to as short as possible. A lower-risk environment might be a foster home that houses only one litter of kittens at a time, who are kept in an environment that is amenable to disinfection between kittens or groups of kittens, and with no history of panleukopenia in previous fosters. For these kittens, a 3-4 week inter-vaccination interval, similar to owned kittens in a home, may be adequate. 

Keep in mind that a low-risk environment can quickly change to high-risk when kittens are brought back to the shelter for spay/neuter or adoption. When possible, vaccination at least 3-5 days prior to return is a good idea to provide as much protection as possible before re-entering the shelter. But despite the most diligent vaccination practices kittens < 20 weeks of age in shelters are still vulnerable to infectious diseases such as panleukopenia. The most effective way to reduce this risk, in addition to vaccination, is to shorten their time spent in the shelter. For this reason (and several other good ones) our recommendation for healthy kittens would be to spay/neuter/adopt as early as 6 weeks of age and foster care for those younger than 6 weeks. See more about the recommendation for this in Dr. Aziz' blog post for the Million Cat Challenge.

Deb Yannessa, DVM

Maddie’s Shelter Medicine Intern

Shelter Medicine Program

University of Wisconsin – Madison

School of Veterinary Medicine

www.uwsheltermedicine.com
www.facebook.com/uwsheltermedicine