COVID-19 Vaccine

Inclusion Criteria

• Are aged 18 years and older at randomization, have a body mass index over 18.5 kg/m^2 and under 35 kg/m^2, and weigh at least 50 kg at Visit 0.
• n IMP starting from Visit 0 and until 168 days after receiving the last IMP dose. Inclusion criteria pertaining to Dose 2: If 168 days after the participant's first IMP dose had passed before they consent to Dose 2, they should agree to not enroll in another trial from the time of consent to Dose 2 until 168 days after receiving Dose 2 of the IMP.
• Agree not to be vaccinated with:
• Non-trial vaccines (except COVID-19 vaccines, as per next sub-bullet) starting 28 days prior to the Dose 1 and until 28 days after receiving of the last IMP dose. Seasonal influenza vaccine is allowed; however, it should be given at least 14 days before or after any administration of IMP. Inclusion criteria pertaining to Dose 2: If 28 days after the participant's first IMP dose had passed before they consent to continue Dose 2, they should not have been vaccinated with non-trial vaccines starting from the time of consent to Dose 2 and until 168 days after receiving the Dose 2 of the IMP.
• Non-trial COVID-19 vaccines starting at least 90 days prior to the Visit 1 and until completion of the participant's last trial visit.
• Have been vaccinated with at least three doses of an RNA-based COVID-19 vaccine authorized in the United States (US) before Visit 0. The last COVID-19 RNA vaccine dose must have been administered at least 90 days before Visit 1.
• Note: Documented confirmation of prior COVID-19 vaccine receipt must be obtained prior to randomization.

Exclusion Criteria:

• History of any severe adverse reactions to vaccines or to vaccine components and including history of anaphylaxis and related symptoms such as hives, respiratory difficulty, angioedema, and/or abdominal pain. (Not excluded from participation: a volunteer who had an anaphylactic adverse reaction to pertussis vaccine as a child).
• Current or history of the following medical conditions:
• Uncontrolled or moderate or severe respiratory diseases (e.g., asthma, chronic obstructive pulmonary disease); symptoms of asthma severity as defined in the most recent US National Heart, Lung, and Blood Institute asthma management guidelines.
• Diabetes mellitus type 1 or type 2, or new onset of Diabetes mellitus type 1 or 2 from the administration of Dose 1, including cases controlled with diet alone (Not excluded: history of isolated gestational diabetes).
• Hypertension:
• If a person has been found to have elevated blood pressure or hypertension during screening or previously, exclude for blood pressure that is not well controlled. Well controlled blood pressure is defined as consistently ≤140 mm Hg systolic and ≤90 mm Hg diastolic, with or without medication, with only isolated, brief instances of higher readings, which must be ≤150 mm Hg systolic and ≤90 mm Hg diastolic at Visit 0.
• If a person does not have a history of elevated blood pressure or hypertension previously or during screening, also exclude for systolic blood pressure ≥150 mm Hg at Visit 0 or diastolic blood pressure ≥100 mm Hg at Visit 0. Exclusion pertaining to Dose 2: Participants who have new onset of worsening hypertension since enrollment, that, in the opinion of the investigator would constitute an increased risk to the individual's participation in Dose 2.
• Any current or history of cardiovascular diseases such as myocarditis, pericarditis, myocardial infarction, symptomatic congestive heart failure, cardiomyopathy or clinically significant arrhythmias. Exclusion pertaining to Dose 2: Participants who have new onset of cardiovascular disease since enrollment, that, in the opinion of the investigator would constitute an increased risk to the individual's participation in Dose 2.
• A diagnosed bleeding disorder (e.g., factor deficiency, coagulopathy, or platelet disorder requiring special precautions). Exclusion pertaining to Dose 2: Participants who have new onset of a bleeding disorder since enrollment, that, in the opinion of the investigator, would constitute an increased risk to the individual's participation in Dose 2.
• Seizure disorders: History of seizure(s) within the past 3 years. Also exclude if volunteer has used medications in order to prevent or treat seizure(s) at any time within the past 3 years.
• Screening 12-lead ECG that is consistent with probable or possible myocarditis or pericarditis, or demonstrates clinically relevant abnormalities that may affect participant safety or interpretation of the trial results. Exclusion pertaining to Dose 2: Only symptomatic participants or whose clinical picture, in the opinion of the investigator, warrant ECG will have a repeat 12-lead ECG prior to Dose 2.