SWIM-816

Primary Immunogenicity Objective：Cohort 1: GMTs of SARS-CoV-2 Omicron and related strain neutralizing antibody levels for SWIM816.Cohort 2: To demonstrate the non- inferiority of neutralizing antibody response in terms of geometric mean titers (GMT) of COVID-19 mRNA vaccine(SWIM816) compare with mRNA COVID-19 vaccine(Pfizer Bivalent vaccine) 14 days post dose.
Primary Safety Objective：To assess the reactogenicity and safety of a booster dose in a heterologous vaccination regimen in subjects previously immunized with 2/3 doses of COVID-19 vaccine with or without previously diagnosed with COVID-19.
Secondary Immunogenicity Objectives：To describe the neutralizing antibody response at D29, D91 and D181.To describe binding antibody profile at D01, D15, D29, D91 and D181 of each study group.
Secondary Safety Objective：To assess the reactogenicity and safety of third or fourth booster dose in a heterologous vaccination regimen in subjects previously immunized with 2/3 COVID-19 vaccine doses.
Exploratory Objective：1.Documented confirmed SARS-CoV-2 symptomatic infection；2.Todemonstrate the cellular immune response profile at study group (30 subjects per each group for cellular immune testing).