Question: 

Our rescue partner is advising us to use only 1/2 a dose of the SQ FVRCP vaccine for the 6 week old kittens (Splitting 1 vial between 2 kittens).  I have found the recommendation AGAINST splitting dog vaccines in the 2011 AAHA Canine Vaccination Guidelines, but can't find a reference against splitting  cat vaccines.  I am uncomfortable using only 1/2 a dose on the kittens without a reference to back this up.  Cost is not a factor as we get our vaccines very affordably through the Zoetis for shelters program (The cat vaccine is just over $1 a dose).

Answer Date: 
June 16, 2014

Answer: 

You are correct regarding the recommendation AGAINST splitting vaccines.  This is applicable for both dog and cat vaccines.  The idea behind the recommended vaccine dose is that it contains what has been determined to be the minimum amount of antigen needed to adequately stimulate the immune system - regardless of the pet's size.  If you do not administer the vaccine properly (route, dosage), then not only can this result in vaccine failure but it also negates the manufacturer's warranty regarding the efficacy of the vaccine.  
 
Regarding references: it is difficult to locate primary references since these concepts were validated in studies done some time ago.  I did find two references that might help you though - one is a recent publication, "2013 update on current vaccination strategies in puppies and kittens" by GM Davis-Wurzler (Vet Clin North Am Small Anim Pract. 2014 Mar;44(2):235-63.).  Here is the applicable quote from this publication:
 
"The practitioner is advised to always follow the manufacturer’s directions for dose and route of administration. Using a topical product parenterally or splitting doses should never be done. A full dose is required to stimulate the immune system; there is no medical basis for giving a smaller dose to a toy breed dog, and this practice could lead to vaccine failure in that animal. If done with a rabies vaccine the practitioner is not following federal requirements, which carries potential legal implications."
 
Also, WSAVA (the World Small Animal Veterinary Association) publishes vaccination guidelines for cats and dogs and under its FAQ section it states,
 
"26. May I use smaller vaccine doses in small breeds to reduce the risk of adverse reactions?
No. The volume (e.g. 1.0 ml) as recommended by the manufacturer generally represents the minimum immunizing dose, therefore the total amount must be given."
 
(http://www.wsava.org/sites/default/files/VaccinationGuidelines2010.pdf)
 
I hope this helps,

Chumkee Aziz, DVM
Resident, Koret Shelter Medicine Program
Center for Companion Animal Health
UC Davis School of Veterinary Medicine

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