Safety and immunogenicity of a mutagenized, live attenuated Rift Valley fever vaccine, MP-12, in a Phase 1 dose escalation and route comparison study in humans.

•A single dose of RVF MP-12 vaccine, delivered intramuscularly or subcutaneously, was well tolerated by human volunteers.•Low-titer viremia was detected via amplification in six subjects and via direct plaque assay in one subject.•Over the course of the study, 93% of vaccinees (40 of 43) achieved neutralizing antibodies and RVF-specific IgM and IgG.•Among vaccinees tested 1 year after vaccination, 82% remained seropositive.