This is a Phase I, prospective, randomized, open-labeled study to evaluate the safety, tolerability, and immunogenicity of a booster vaccination with the MVC-COV1901 or MVC1901(Beta). Approximately 120 participants aged ≥18 and <55 years, who received two or three doses of MVC- COV1901 vaccines, will be enrolled and divided into two groups. Each group will consist of approximately 60 eligible subjects, and for each group the randomization will be stratified based on site to three treatment arms (15 mcg of MVC-COV1901 or 15 mcg or 25 mcg of MVC-COV1901(Beta) in 1:1:1 ratio).
The purpose of this study is to assess the safety, tolerability, and immunogenicity of a booster dose of vaccine in participants who are generally healthy or with stable pre-existing health conditions. Study details include:~The study duration per participant will be approximately 209 days (28 days screening, 1 day vaccination, and 180 days follow-up).~The treatment duration will be 1 day. -The visit frequency will be 6 on-site visits (1 screening visit, 1 treatment visit, and 4 follow- up visits) and 1 phone visit.