Arcturus Therapeutics Holdings Inc. reported that ARCT-154, its self-amplifying mRNA COVID-19 vaccine, showed efficacy of 55% against infection and 95% efficacy against severe disease, meeting the primary and key secondary endpoints of the ongoing phase I/II/III trial. While the company’s stock (NASDAQ:ARCT) regained much of its initial 25% drop to close the day, investors continue to await further data to determine where Arcturus’ vaccine will fit in with available COVID-19 vaccines.