Pittman PR, Hahn M, Lee HS, et al. - A total of 440 individuals were randomized to receive two doses of modified vaccinia Ankara (MVA) followed by one dose of the established replicating-vaccinia vaccine ACAM2000 (the MVA group) or to receive one dose of ACAM2000 (the ACAM2000-only group) in order to assess the efficiency of MVA as a potential smallpox vaccine. A total of 220 and 213 persons were randomized and vaccinated in the MVA group and ACAM2000-only group, respectively, and 208 received two MVA vaccinations. No safety matters related to the MVA vaccine were recognized. Moreover, immune responses and attenuation of the principal cutaneous reaction imply that this MVA vaccine shielded against variola infection.