1. Male or female, at least 16 years of age at the time of consent (Screening Visit) 2. Investigator’s assessment that participant understands and is willing and physically able to comply with protocol-mandated follow-up, including all procedures 3. Participant has provided written informed consent for participation in this study, including all evaluations and procedures as specified in this protocol 4. Female participants of nonchildbearing potential may be enrolled in the study. Nonchildbearing potential is defined as bilateral tubal ligation > 1 year prior to the Screening Visit, bilateral oophorectomy, hysterectomy, or postmenopausal (defined as amenorrhea for = 12 consecutive months prior to the Screening Visit without an alternative medical cause). A follicle stimulating hormone (FSH) level may be measured at the discretion of the investigator to confirm postmenopausal status 5. Female participants of childbearing potential may be enrolled in the study if the participant fulfills all the following criteria: 5.1 Has a negative pregnancy test at the Screening Visit and on the day of vaccination prior to vaccine dose being administered on Day 1. 5.2 Has practiced adequate contraception or has abstained from all activities that could result in pregnancy for at least 28 days prior to the first dose (Day 1). Adequate female contraception is defined as consistent and correct use of a local health authority approved contraceptive method in accordance with the product label. 5.3 Has agreed to continue adequate contraception through 90 days following vaccine administration 6. Has received 2 prior doses of one of the following approved/authorized COVID-19 vaccines: Moderna, Pfizer/BioNTech, Oxford/AstraZeneca, Janssen. A heterologous vaccine regimen is acceptable 7. Participants who will receive the 4th dose as part of the study must have previously received a mRNA vaccine (Moderna or Pfizer/BioNTech) as the 3rd dose of a COVID-19 vaccine. Participants who will receive the 3rd dose as part of the study may have previously received 2 doses of an approved/authorized mRNA or a non-mRNA COVID-19 vaccine (a heterologous vaccine regimen is acceptable).

1. Male or female, at least 16 years of age at the time of consent (Screening Visit) 2. Investigator’s assessment that participant understands and is willing and physically able to comply with protocol-mandated follow-up, including all procedures 3. Participant has provided written informed consent for participation in this study, including all evaluations and procedures as specified in this protocol 4. Female participants of nonchildbearing potential may be enrolled in the study. Nonchildbearing potential is defined as bilateral tubal ligation > 1 year prior to the Screening Visit, bilateral oophorectomy, hysterectomy, or postmenopausal (defined as amenorrhea for = 12 consecutive months prior to the Screening Visit without an alternative medical cause). A follicle stimulating hormone (FSH) level may be measured at the discretion of the investigator to confirm postmenopausal status 5. Female participants of childbearing potential may be enrolled in the study if the participant fulfills all the following criteria: 5.1 Has a negative pregnancy test at the Screening Visit and on the day of vaccination prior to vaccine dose being administered on Day 1. 5.2 Has practiced adequate contraception or has abstained from all activities that could result in pregnancy for at least 28 days prior to the first dose (Day 1). Adequate female contraception is defined as consistent and correct use of a local health authority approved contraceptive method in accordance with the product label. 5.3 Has agreed to continue adequate contraception through 90 days following vaccine administration 6. Has received 2 prior doses of one of the following approved/authorized COVID-19 vaccines: Moderna, Pfizer/BioNTech, Oxford/AstraZeneca, Janssen. A heterologous vaccine regimen is acceptable 7. Participants who will receive the 4th dose as part of the study must have previously received a mRNA vaccine (Moderna or Pfizer/BioNTech) as the 3rd dose of a COVID-19 vaccine. Participants who will receive the 3rd dose as part of the study may have previously received 2 doses of an approved/authorized mRNA or a non-mRNA COVID-19 vaccine (a heterologous vaccine regimen is acceptable).