Comparison of the safety and immunogenicity of ACAM1000, ACAM2000 and Dryvax® in healthy vaccinia-naive adults

Currently, more than half of the world's population has no immunity against smallpox variola major virus. This phase I double-blind, randomized trial was conducted to compare the safety and immunogenicity of two clonally derived, cell-culture manufactured vaccinia strains, ACAM1000 and ACAM2000, to the parent vaccine, Dryvax®. Thirty vaccinia-naïve subjects were enrolled into each of three groups and vaccines were administered percutaneously using a bifurcated needle at a dose of 1.0 × 108 PFU/mL. All subjects had a primary skin reaction indicating a successful vaccination. The adverse events, 4-fold neutralizing antibody rise and T cell immune responses were similar between the groups.