A Safety and Immune Response Study to Evaluate Varying Doses of an mRNA Vaccine Against Coronavirus Disease 2019 (COVID-19) in Healthy Adults

Inclusion Criteria

• Written or witnessed informed consent obtained from the participant prior to performance of any study-specific procedure.
• Participants, who in the opinion of the investigator, can and will comply with the requirements of the protocol (e.g., completion of the eDiary and study procedures).
• Has received 2 doses of primary series and booster dose(s) of an authorized or licensed mRNA COVID-19 vaccine (only Moderna or Pfizer vaccines) with the last booster dose administered between at least 6 and 18 months or more prior to screening and has provided documentation of receiving the vaccination series (e.g., vaccination card).
• Negative for SARS-CoV-2 infection by RT-PCR test at screening within 7 days prior to study vaccination.
• Is a male or nonpregnant female of 18 to 49 years, inclusive, at screening.
• If the participant is a woman of childbearing potential (WOCBP), the participant agrees to practice true abstinence or use at least 1 highly effective form of contraception for at least 30 days prior to study vaccination up to 1 month after study vaccination.
• Agrees to refrain from blood or plasma donation from screening and up to 6 months after vaccination.
• Is healthy or medically stable as determined by investigator judgment based on medical history, clinical laboratory tests, vital sign measurements, and physical examination findings.

Exclusion Criteria

• Has a new onset, clinically significant, abnormal biochemistry or hematology finding [defined as greater than or equal to (>=) Grade 1] at screening (participants with Grade 1 laboratory abnormalities that have been stable for at least 6 months before enrollment may be included in the study).
• Has any medical disease or condition that, in the opinion of the investigator, precludes study participation. This includes any acute, subacute, intermittent, or chronic medical disease or condition that would place the participant at an unacceptable risk of injury, render the participant unable to meet the requirements of the protocol, or may interfere with the evaluation of responses or the participant's successful completion of the trial.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required).
• History of myocarditis, pericarditis, second- and third-degree heart block or idiopathic cardiomyopathy, or presence of any medical condition that increases risk of myocarditis or pericarditis, including cocaine abuse, cardiomyopathy, endomyocardial fibrosis, hypereosinophilic syndrome, hypersensitivity myocarditis eosinophilic granulomatosis with polyangiitis, persistent myocardial viral infection (e.g., due to enterovirus or adenovirus).
• Has an acute febrile illness with a temperature >=38.0 degree Celsius (°C) or >=100.4 degree Fahrenheit (°F) observed by the participant or at the study site within 72 hours prior to study vaccination. Participants with suspected COVID-19 symptoms should be excluded and referred for medical care.
• Has a history of hypersensitivity or severe allergic reaction, including anaphylaxis, generalized urticaria, angioedema, and other significant reactions to any previous vaccine, or any component of the study vaccine.
• Has a body mass index greater than (>) 40 Kilograms meter per square (kg/m^2).
• Has had known close contact with anyone who had a confirmed SARS-CoV-2 infection within 14 days before study vaccination.
• Has a history of documented SARS-CoV-2 infection or COVID-19 within 6 months before the date of screening visit.
• Has any self-reported or medically documented clinically significant medical or psychiatric condition. Significant medical conditions include, but are not limited to, the following:
• Moderate or severe respiratory disease (e.g., chronic obstructive pulmonary disease, asthma).
• Uncontrolled hypertension, defined as an average systolic blood pressure >= 140 millimeters of me