In prior trials evaluating alternative methods of vaccine administration, scarification has been found to be an imprecise method of administration and allows only 1.0 - 2.5 microliters of immunogen to be given. Since it is not feasible to produce vaccine at concentrations higher than 10 to the 10th pfu/ml, this method limits the maximum deliverable dose. Intradermal and subcutaneous injection routes allow larger volumes of vaccinia to be given, i.e.: up to 200 microliters intradermally and up to 100 ml subcutaneously. In the present study, the initial priming dose will be the same administered by all 3 methods; however, the second priming dose administered at 2 months intradermally and subcutaneously will be 2 logs higher in order to achieve boosting of immune responses, particularly to gag and pol components of TBC-3B.