Page K, Melia MT, Veenhuis RT, et al. - Researchers designed a phase 1–2 randomized, double-blind, placebo-controlled trial to investigate a recombinant chimpanzee adenovirus 3 vector priming vaccination followed by a recombinant modified vaccinia Ankara boost; both vaccines encode hepatitis C virus (HCV) nonstructural proteins. They randomized adults thought to be at risk for HCV infection on the basis of a history of recent injection drug use in a 1:1 ratio to receive vaccine or placebo on days 0 and 56. For the analysis, a total of 548 participants had undergone randomization, with 274 assigned to each group. It was shown that the HCV vaccine regimen did not cause serious adverse events, produced HCV-specific T-cell responses, and lowered the peak HCV RNA level, but it did not prevent chronic HCV infection, as the incidence of chronic HCV infection between the groups did not differ significantly.