A Study to Evaluate Efficacy, Safety, and Immunogenicity of mRNA-1273 Vaccine in Adults Aged 18 Years and Older to Prevent COVID-19

This is a 3-part Phase 3 study, with Part A (Blinded Phase), Part B (Open-label Observational Phase), and Part C (Booster Dose Phase). Participants in Part A are blinded to their treatment assignment, with participants receiving either mRNA-1273 vaccine or placebo. Part B of the study is designed to offer participants to be unblinded so that participants who received placebo in Part A can request 2 doses of open-label mRNA-1273 vaccine. Additionally, participants who choose to be unblinded and were only able to receive 1 dose of mRNA-1273 due to administrative reasons, can choose to receive the second dose of mRNA-1273 during Part B. In Part C, a booster dose will be provided for all eligible participants who choose to receive one. Please access www.modernatx.com/cove-study for additional information, such as Study Overview, Participation, and Site Locations along with contact numbers for each location for the study.