APSV in Vaccinia Naive Adults

The study seeks to define, with precision, the safety and efficacy of APSV, two dose potencies of one lot in vaccinia-naive adults. The ability of this vaccine to induce a classic �take� as defined by formation of a lesion at the injection site consistent with the �Jennerian� process (see Appendix A) and vaccine specific immune responses will be assessed. The local cutaneous lesion is considered to be a surrogate for clinical effectiveness of live, replicating smallpox vaccines. Neutralizing antibody formation has been correlated with takes for the Dryvax vaccine and is considered to be cross-protective for other orthopoxviruses, including variola. The study also seeks to characterize preliminarily the cell mediated immune (CMI) response to APSV (as compared to Dryvax).