inclusion criteria: in order to be eligible to participate in this study, a subject must meet all of the following criteria: * age 18-85 years (extremes included), males and females. * negative sars-cov-2 serology (an anti-sars-cov-2 sp-specific igg elisa) * body mass index (bmi) between 19.0 and 30.0 kg/m2, inclusive * general good health, without significant medical illness, as determined via physical exam findings, or vital signs * no clinically significant laboratory abnormalities as determined by the investigator o note: one retest of lab tests is allowed within the screening window * informed consent form signed voluntarily before any study-related procedure is performed, indicating that the subject understands the purpose and procedures required for the study and is willing to participate in the study * willing to adhere to the prohibitions and restrictions specified in this protocol * all participants have received a completed (registered) vaccine at least 3 months before inclusion in this study (i.e. pfizer \[comirnaty\], moderna \[spikevax\], janssen \[ad26.cov2.s\], astrazeneca \[vaxzevria\]). * negative hepatitis panel (including hepatitis b surface ag and anti-hepatitis c virus abs) and negative human immunodeficiency virus ab and ag screens at screening * female subjects should fulfil one of the following criteria: * at least 1 year post-menopausal (amenorrhea \>12 months * surgically sterile (bilateral oophorectomy, hysterectomy, or tubal ligation); * will use adequate forms of contraceptives from screening to discharge. * female subjects of childbearing potential and male subjects who are sexually active with a female partner of childbearing potential must agree to the use of an effective method of birth control from screening to discharge o note: medically acceptable methods of contraception that may be used by the subject and/or partner include combined oral contraceptive, contraceptive vaginal ring, contraceptive injection, intrauterine device, etonogestrel implant, double barrier, sterilization and vasectomy * female subject has a negative pregnancy test at screening and upon check-in at the clinical site. * note: pregnancy testing will consist of a serum pregnancy test at screening and urine pregnancy tests at the dosing visit, in all women.

inclusion criteria: in order to be eligible to participate in this study, a subject must meet all of the following criteria: * age 18-85 years (extremes included), males and females. * negative sars-cov-2 serology (an anti-sars-cov-2 sp-specific igg elisa) * body mass index (bmi) between 19.0 and 30.0 kg/m2, inclusive * general good health, without significant medical illness, as determined via physical exam findings, or vital signs * no clinically significant laboratory abnormalities as determined by the investigator o note: one retest of lab tests is allowed within the screening window * informed consent form signed voluntarily before any study-related procedure is performed, indicating that the subject understands the purpose and procedures required for the study and is willing to participate in the study * willing to adhere to the prohibitions and restrictions specified in this protocol * all participants have received a completed (registered) vaccine at least 3 months before inclusion in this study (i.e. pfizer \[comirnaty\], moderna \[spikevax\], janssen \[ad26.cov2.s\], astrazeneca \[vaxzevria\]). * negative hepatitis panel (including hepatitis b surface ag and anti-hepatitis c virus abs) and negative human immunodeficiency virus ab and ag screens at screening * female subjects should fulfil one of the following criteria: * at least 1 year post-menopausal (amenorrhea \>12 months * surgically sterile (bilateral oophorectomy, hysterectomy, or tubal ligation); * will use adequate forms of contraceptives from screening to discharge. * female subjects of childbearing potential and male subjects who are sexually active with a female partner of childbearing potential must agree to the use of an effective method of birth control from screening to discharge o note: medically acceptable methods of contraception that may be used by the subject and/or partner include combined oral contraceptive, contraceptive vaginal ring, contraceptive injection, intrauterine device, etonogestrel implant, double barrier, sterilization and vasectomy * female subject has a negative pregnancy test at screening and upon check-in at the clinical site. * note: pregnancy testing will consist of a serum pregnancy test at screening and urine pregnancy tests at the dosing visit, in all women.

inclusion criteria: in order to be eligible to participate in this study, a subject must meet all of the following criteria: age 18-85 years (extremes included), males and females. negative sars-cov-2 serology (an anti-sars-cov-2 sp-specific igg elisa) body mass index (bmi) between 19.0 and 30.0 kg/m2, inclusive general good health, without significant medical illness, as determined via physical exam findings, or vital signs no clinically significant laboratory abnormalities as determined by the investigator o note: one retest of lab tests is allowed within the screening window informed consent form signed voluntarily before any study-related procedure is performed, indicating that the subject understands the purpose and procedures required for the study and is willing to participate in the study willing to adhere to the prohibitions and restrictions specified in this protocol all participants have received a completed (registered) vaccine at least 3 months before inclusion in this study (i.e. pfizer [comirnaty], moderna [spikevax], janssen [ad26.cov2.s], astrazeneca [vaxzevria]). negative hepatitis panel (including hepatitis b surface ag and anti-hepatitis c virus abs) and negative human immunodeficiency virus ab and ag screens at screening female subjects should fulfil one of the following criteria: at least 1 year post-menopausal (amenorrhea >12 months surgically sterile (bilateral oophorectomy, hysterectomy, or tubal ligation); will use adequate forms of contraceptives from screening to discharge. female subjects of childbearing potential and male subjects who are sexually active with a female partner of childbearing potential must agree to the use of an effective method of birth control from screening to discharge o note: medically acceptable methods of contraception that may be used by the subject and/or partner include combined oral contraceptive, contraceptive vaginal ring, contraceptive injection, intrauterine device, etonogestrel implant, double barrier, sterilization and vasectomy female subject has a negative pregnancy test at screening and upon check-in at the clinical site. note: pregnancy testing will consist of a serum pregnancy test at screening and urine pregnancy tests at the dosing visit, in all women.

inclusion criteria: in order to be eligible to participate in this study, a subject must meet all of the following criteria: age 18-85 years (extremes included), males and females. negative sars-cov-2 serology (an anti-sars-cov-2 sp-specific igg elisa) body mass index (bmi) between 19.0 and 30.0 kg/m2, inclusive general good health, without significant medical illness, as determined via physical exam findings, or vital signs no clinically significant laboratory abnormalities as determined by the investigator o note: one retest of lab tests is allowed within the screening window informed consent form signed voluntarily before any study-related procedure is performed, indicating that the subject understands the purpose and procedures required for the study and is willing to participate in the study willing to adhere to the prohibitions and restrictions specified in this protocol all participants have received a completed (registered) vaccine at least 3 months before inclusion in this study (i.e. pfizer [comirnaty], moderna [spikevax], janssen [ad26.cov2.s], astrazeneca [vaxzevria]). negative hepatitis panel (including hepatitis b surface ag and anti-hepatitis c virus abs) and negative human immunodeficiency virus ab and ag screens at screening female subjects should fulfil one of the following criteria: at least 1 year post-menopausal (amenorrhea >12 months surgically sterile (bilateral oophorectomy, hysterectomy, or tubal ligation); will use adequate forms of contraceptives from screening to discharge. female subjects of childbearing potential and male subjects who are sexually active with a female partner of childbearing potential must agree to the use of an effective method of birth control from screening to discharge o note: medically acceptable methods of contraception that may be used by the subject and/or partner include combined oral contraceptive, contraceptive vaginal ring, contraceptive injection, intrauterine device, etonogestrel implant, double barrier, sterilization and vasectomy female subject has a negative pregnancy test at screening and upon check-in at the clinical site. note: pregnancy testing will consist of a serum pregnancy test at screening and urine pregnancy tests at the dosing visit, in all women.