I have always wondered how a rabies vaccine could be good for 1 or 3 years. In commercial vaccines, modified-live virus vaccines seem to produce stronger reactions and longer immunity. A vaccine is not simply a liquid form of killed virus in water but is a slurry of vaccine and other chemical agents. This gives the lengthened time of immune response and the difference between vaccine immunity protection times.
Different adjuvants give different immune times, and also different side effects.
There are also new adjuvants that utilize an increased production of cytokines to provide strengthened immunity. Page last updated April 1, 1997.