Safety and immunogenicity of a modified vaccinia Ankara vaccine using three immunization schedules and two modes of delivery: A randomized clinical non-inferiority trial.

•Modified vaccinia Ankara (MVA) vaccine may be used in the event of a smallpox release.•Two doses required, current schedule is administration on Days 1 and 29.•More compressed schedule (Days 1 and 15 or Days 1 and 22) may allow more rapid immunity.•Use of jet injectors (JI) for administration may be beneficial for mass vaccination.•PRNT responses do not support condensed schedules or JI administration.