|I have always wondered how a rabies vaccine could be good for 1
or 3 years. If it is stimulating the immune system to produce
antibodies, how would one last longer than the other? It can't
be a time released thing in the body, can it?| This has to do
with something called "adjuvants" that are present in the
vaccine. A vaccine is not simply a liquid form of killed virus
in water but is a slurry of vaccine and other chemical agents.
If you kill the virus, the body produces an immune response to
the antigen but it can be very weak (since the virus is already
dead) and not provide a long-standing immunity. Drug companies
have found that you can add certain chemicals to the mixture
(like aluminum salt), and they will sequester portions of the
vaccine component, slowing its release to the body. This is the
sort of "time release" we are famililar with in our cold
medications. The adjuvants then act as a "depot" for the
vaccine, as it released slowly into the dog's circulation from
the site of the injection. This gi