5. For Group 6: subjects must have documented previous vaccination with MVA-BN. In order to be enrolled, a subject has to have received two 1 x 10^8 TCID50 doses of MVA-BN 19-45 days apart SC or IM as part of participation in DMID vaccine trials 11-0021 or 09-0002. First dose must have been administered no earlier than 2010.