A Phase I/IIa (dose-escalation, single-center, open-label, Phase I and randomized, observer-blind, multi-center, placebo-controlled, Phase IIa) study to determine safety, tolerance and immunogenicity of a preventive COVID-19 vaccine ‘mRNA SARS-CoV-2 Vaccine (EG-COVID)’ in healthy adult

INTERVENTION: Biological/Vaccine, Non‐Stem Cell : Low‐dose group: EG‐COVID 0.25mL(mRNA 50 µg) Mid‐dose group: EG‐COVID 0.50mL(mRNA 100 µg) High‐dose group: EG‐COVID 0.50mL(mRNA 200 µg) CONDITION: Certain infectious and parasitic diseases PRIMARY OUTCOME: Solicited Adverse Events recorded up to 1st and 2nd vaccination SRR, GMT, GMFR in SARS‐CoV‐2 serum neutralizing titers from before vaccination to each subsequent time point SECONDARY OUTCOME: T cell response ratio in ICS assay from before vaccination to each subsequent time point INCLUSION CRITERIA: 1. provide written informed consent before the first study‐specific procedure ‐ 19 54 years, Male and Female (Step 1 (Phase I)) ‐ 19 85 years, Male and Female (Step 2 (Phase IIa)) 2. Participants must have a body mass index (BMI) between =18.5 and =30.0 kg/m2 at screening 3. Must agree to use highly effective, medically accepted double‐barrier contraception (both male and female partners) from screening until study completion (until 3 months after second vaccination) as specified below in this criterion 4. Must agree not to donate blood or transfusion (including whole blood, plasma, and platelet components)