A Study to Evaluate the Immunogenicity and Safety of Omicron Variant Vaccines in Comparison With mRNA-1273 Booster Vaccine for COVID-19

Participant had close contact (without personal protective equipment \[PPE\]) as defined by the Centers for Disease Control and Prevention (CDC) in the past 14 days to someone diagnosed with SARS-CoV-2 infection or COVID-19 within 10 days of the close contact. Participants may be rescreened after 14 days provided that they remain asymptomatic.

Participant is acutely ill or febrile (temperature ≥ 38.0°C/100.4°F) 72 hours prior to or at the Screening Visit or Day 1.

Participant has tested positive for SARS-CoV-2 by an authorized/approved lateral flow/rapid antigen or polymerase chain reaction (PCR) test within 90 days of Screening.

Participant has received a COVID-19 vaccine within 90 days of the Screening Visit.

Participant has received a total of 4 doses or more of COVID-19 vaccine.

Participant has received a COVID-19 vaccine at a dose different from the authorized/approved dose.

Any medical, psychiatric, or occupational condition, including reported history of substance abuse, that, in the opinion of the Investigator, might pose additional risk due to participation in the study or could interfere with the interpretation of study results.

Participant has received systemic immunosuppressants or immune-modifying drugs for \>14 days in total within 181 days prior to screening (for corticosteroids ≥10 milligrams \[mg\]/day of prednisone or equivalent) or is anticipating the need for immunosuppressive treatment at any time during participation in the study.

Participant has received or plans to receive any licensed vaccine ≤28 days prior to the study injection (Day 1) or plans to receive a licensed vaccine within 28 days after the study injection (with the exception that approved seasonal influenza vaccine may be received by at least 7 days and preferably 14 days apart from the study injection).

Participant has received systemic immunoglobulins or blood products within 90 days prior to the Screening Visit or plans to receive during the study.

Participant has donated ≥450 milliliters (mL) of blood products within 28 days prior to the Screening Visit or plans to donate blood products during the study.

Participant has participated in an interventional clinical study within 28 days prior to the Screening Visit based on the medical history interview or plans to do so while participating in this study.

What this study is about