inclusion criteria: * seronegative (group 1): negative qualitative test for sars-cov-2 antibodies at scr. seropositive (group 2 and group 3): previous covid-19 disease or previously completed vaccination regimen with an authorized sars-cov-2 vaccine at least 90 days before planned trial vaccination and a positive qualitative test for sars-cov-2 antibodies at scr. "authorized" sars-cov-2 vaccine refers to authorization status at scr, i.e., subjects can be eligible if the subject previously received investigational vaccines that have since been authorized for emergency use or granted full market licensure. receipt of a single dose of an authorized covid-19 vaccine regimen in subjects with a previous diagnosis of covid-19 or a mix/match series of 2 doses of any authorized covid-19 vaccine will be considered as a completed vaccination. * general good health, without acute medical illness, physical exam findings, or laboratory abnormalities, as determined by the investigator. * body mass index (bmi) ≥18.5 and \<40. * female subjects of childbearing potential (wocbp) must agree to the use of an effective method of birth control from at least 30 days prior to administration of the vaccine until 30 days after the vaccination. male subjects who are sexually active with a wocbp must agree to the use of an effective method of birth control from the day of administration of the vaccine until 30 days after the vaccination. * negative human immunodeficiency virus antibody test (anti hiv), negative hepatitis b surface antigen (hbsag) and negative antibody to hepatitis c virus (hcv).

inclusion criteria: * seronegative (group 1): negative qualitative test for sars-cov-2 antibodies at scr. seropositive (group 2 and group 3): previous covid-19 disease or previously completed vaccination regimen with an authorized sars-cov-2 vaccine at least 90 days before planned trial vaccination and a positive qualitative test for sars-cov-2 antibodies at scr. "authorized" sars-cov-2 vaccine refers to authorization status at scr, i.e., subjects can be eligible if the subject previously received investigational vaccines that have since been authorized for emergency use or granted full market licensure. receipt of a single dose of an authorized covid-19 vaccine regimen in subjects with a previous diagnosis of covid-19 or a mix/match series of 2 doses of any authorized covid-19 vaccine will be considered as a completed vaccination. * general good health, without acute medical illness, physical exam findings, or laboratory abnormalities, as determined by the investigator. * body mass index (bmi) ≥18.5 and \<40. * female subjects of childbearing potential (wocbp) must agree to the use of an effective method of birth control from at least 30 days prior to administration of the vaccine until 30 days after the vaccination. male subjects who are sexually active with a wocbp must agree to the use of an effective method of birth control from the day of administration of the vaccine until 30 days after the vaccination. * negative human immunodeficiency virus antibody test (anti hiv), negative hepatitis b surface antigen (hbsag) and negative antibody to hepatitis c virus (hcv).

inclusion criteria: seronegative (group 1): negative qualitative test for sars-cov-2 antibodies at scr. seropositive (group 2 and group 3): previous covid-19 disease or previously completed vaccination regimen with an authorized sars-cov-2 vaccine at least 90 days before planned trial vaccination and a positive qualitative test for sars-cov-2 antibodies at scr. "authorized" sars-cov-2 vaccine refers to authorization status at scr, i.e., subjects can be eligible if the subject previously received investigational vaccines that have since been authorized for emergency use or granted full market licensure. receipt of a single dose of an authorized covid-19 vaccine regimen in subjects with a previous diagnosis of covid-19 or a mix/match series of 2 doses of any authorized covid-19 vaccine will be considered as a completed vaccination. general good health, without acute medical illness, physical exam findings, or laboratory abnormalities, as determined by the investigator. body mass index (bmi) ≥18.5 and <40. female subjects of childbearing potential (wocbp) must agree to the use of an effective method of birth control from at least 30 days prior to administration of the vaccine until 30 days after the vaccination. male subjects who are sexually active with a wocbp must agree to the use of an effective method of birth control from the day of administration of the vaccine until 30 days after the vaccination. negative human immunodeficiency virus antibody test (anti hiv), negative hepatitis b surface antigen (hbsag) and negative antibody to hepatitis c virus (hcv).

inclusion criteria: seronegative (group 1): negative qualitative test for sars-cov-2 antibodies at scr. seropositive (group 2 and group 3): previous covid-19 disease or previously completed vaccination regimen with an authorized sars-cov-2 vaccine at least 90 days before planned trial vaccination and a positive qualitative test for sars-cov-2 antibodies at scr. "authorized" sars-cov-2 vaccine refers to authorization status at scr, i.e., subjects can be eligible if the subject previously received investigational vaccines that have since been authorized for emergency use or granted full market licensure. receipt of a single dose of an authorized covid-19 vaccine regimen in subjects with a previous diagnosis of covid-19 or a mix/match series of 2 doses of any authorized covid-19 vaccine will be considered as a completed vaccination. general good health, without acute medical illness, physical exam findings, or laboratory abnormalities, as determined by the investigator. body mass index (bmi) ≥18.5 and <40. female subjects of childbearing potential (wocbp) must agree to the use of an effective method of birth control from at least 30 days prior to administration of the vaccine until 30 days after the vaccination. male subjects who are sexually active with a wocbp must agree to the use of an effective method of birth control from the day of administration of the vaccine until 30 days after the vaccination. negative human immunodeficiency virus antibody test (anti hiv), negative hepatitis b surface antigen (hbsag) and negative antibody to hepatitis c virus (hcv).

inclusion criteria: - seronegative (group 1): negative qualitative test for sars-cov-2 antibodies at scr. seropositive (group 2): previous covid-19 disease or previously completed vaccination regimen with an authorized sars-cov-2 vaccine at least 3 months before scr, and a positive qualitative test for sars-cov-2 antibodies at scr. "authorized" sars-cov2 vaccine refers to authorization status at scr, i.e., subjects can be eligible if the subject previously received investigational vaccines that have since been authorized for emergency use or granted full market licensure. - general good health, without acute medical illness, physical exam findings, or laboratory abnormalities, as determined by the investigator. - body mass index (bmi) ≥18.5 and <40. - female subjects of childbearing potential (wocbp) must agree to the use of an effective method of birth control from at least 30 days prior to administration of the vaccine until 30 days after the vaccination. male subjects who are sexually active with a wocbp must agree to the use of an effective method of birth control from the day of administration of the vaccine until 30 days after the vaccination. - negative human immunodeficiency virus antibody test (anti hiv), negative hepatitis b surface antigen (hbsag) and negative antibody to hepatitis c virus (hcv).

inclusion criteria: - seronegative (group 1): negative qualitative test for sars-cov-2 antibodies at scr. seropositive (group 2): previous covid-19 disease or previously completed vaccination regimen with an authorized sars-cov-2 vaccine at least 3 months before scr, and a positive qualitative test for sars-cov-2 antibodies at scr. "authorized" sars-cov2 vaccine refers to authorization status at scr, i.e., subjects can be eligible if the subject previously received investigational vaccines that have since been authorized for emergency use or granted full market licensure. - general good health, without acute medical illness, physical exam findings, or laboratory abnormalities, as determined by the investigator. - body mass index (bmi) ≥18.5 and <40. - female subjects of childbearing potential (wocbp) must agree to the use of an effective method of birth control from at least 30 days prior to administration of the vaccine until 30 days after the vaccination. male subjects who are sexually active with a wocbp must agree to the use of an effective method of birth control from the day of administration of the vaccine until 30 days after the vaccination. - negative human immunodeficiency virus antibody test (anti hiv), negative hepatitis b surface antigen (hbsag) and negative antibody to hepatitis c virus (hcv).

inclusion criteria: - seronegative (group 1): negative qualitative test for sars-cov-2 antibodies at scr. seropositive (group 2): previous covid-19 disease or previously completed vaccination regimen with an authorized sars-cov-2 vaccine at least 3 months before scr, and a positive qualitative test for sars-cov-2 antibodies at scr. "authorized" sars-cov2 vaccine refers to authorization status at scr, i.e., subjects can be eligible if they previously received investigational vaccines that have since been authorized for emergency use or granted full market licensure. - general good health, without acute medical illness, physical exam findings, or laboratory abnormalities, as determined by the investigator. - body mass index (bmi) ≥18.5 and <40. - female subjects of childbearing potential (wocbp) must agree to the use of an effective method of birth control from at least 30 days prior to administration of the vaccine until 30 days after the vaccination. male subjects who are sexually active with a wocbp must agree to the use of an effective method of birth control from the day of administration of the vaccine until 30 days after the vaccination. - negative human immunodeficiency virus antibody test (anti hiv), negative hepatitis b surface antigen (hbsag) and negative antibody to hepatitis c virus (hcv).

inclusion criteria: - seronegative (group 1): negative qualitative test for sars-cov-2 antibodies at scr. seropositive (group 2): previous covid-19 disease or previously completed vaccination regimen with an authorized sars-cov-2 vaccine at least 3 months before scr, and a positive qualitative test for sars-cov-2 antibodies at scr. "authorized" sars-cov2 vaccine refers to authorization status at scr, i.e., subjects can be eligible if they previously received investigational vaccines that have since been authorized for emergency use or granted full market licensure. - general good health, without acute medical illness, physical exam findings, or laboratory abnormalities, as determined by the investigator. - body mass index (bmi) ≥18.5 and <40. - female subjects of childbearing potential (wocbp) must agree to the use of an effective method of birth control from at least 30 days prior to administration of the vaccine until 30 days after the vaccination. male subjects who are sexually active with a wocbp must agree to the use of an effective method of birth control from the day of administration of the vaccine until 30 days after the vaccination. - negative human immunodeficiency virus antibody test (anti hiv), negative hepatitis b surface antigen (hbsag) and negative antibody to hepatitis c virus (hcv).