This is a phase I, open-label, dose-escalation clinical study to evaluate the safety, tolerability and immunogenicity of 3 ascending doses of UB-612 COVID-19 vaccine in healthy adults.

Up to 60 subjects (20 subjects per group) will be enrolled into this study. Subjects in each group will be enrolled to receive two doses of UB-612 vaccine at 28-day interval (Day 0 and Day 28).