My rabies antibody titre is >2.0 iu/ml as of 8th dec 2012. For how long will I be protected even in spite of a rabid bite without taking any boosters?

Sure. You literally can be allergic to anything, including any vaccine. A vaccine, like any medicine, is capable of causing serious problems, such as severe allergic reactions. The risk of a vaccine causing serious harm, or death, is extremely small. Serious problems from Rabies Vaccine are very rare. Several brands of Rabies Vaccine are available in the United States, and reactions may vary.