In a single-centre , double-blind phase @/@a study , young volunteers ( aged @-@ years ) were randomly assigned with a computer-generated list in equal numbers to one of eight groups and were given one injection or two injections intramuscularly at an interval of @ weeks of a standard dose ( @ ( @ ) plaque forming units -LSB- pfu -RSB- ) or a ten times lower dose ( @ ( @ ) pfu ) of the MVA-H@-sfMR ( vector encoding the haemagglutinin gene of influenza A/Vietnam/@ / @ virus -LSB- H@N@ subtype -RSB- ) or MVA-F@-sfMR ( empty vector ) vaccine .