<qa>  What is the vaccine vector used in this trial?HIV-1 presents several challenges to vaccine design, including: 1 high mutation rates resulting in tremendous diversity of virus envelope, the target of neutralizing antibody, such that antibody elicited to one envelope may not protect from virus with a distinct envelope; 2 envelope from infected persons differs from envelopes obtained from T-cell line cultures, the usual source of envelope for vaccines; and 3 envelope glycoprotein exists as oligomers on the virion surface, not as the monomers used in previous vaccines. This study will test a new vaccine that has been designed to meet these challenges by delivering diverse, patient-derived, oligomeric envelopes to induce multiple type-specific responses capable of recognizing native envelope on natural variants. The vaccine vector used in this vaccine trial is recombinant vaccinia virus based on the NYCDH vaccinia isolate. 