inclusion criteria: * is in overall good health based on medical history, physical examination, and vital sign (vs) measurements performed prior to randomization, as assessed by the investigator. * is in overall good health based on laboratory safety tests obtained at the screening visit. * has a body mass index (bmi) ≤30 kg/m2 inclusive (after rounding to the nearest whole number). * parts 1 and 2 (panels a-h) only: has negative testing for severe acute respiratory syndrome coronavirus 2 (sars-cov-2) based on both antibody and reverse transcription polymerase chain reaction (rt-pcr), at screening and upon start of domiciling. * part 3 (panel i) only: has positive serology (antibody) testing for sars-cov-2, also with negative sars cov-2 rt-pcr testing at screening and upon start of domiciling, and without symptoms of respiratory infection for at minimum 3 weeks preceding screening. * has been practicing social distancing for at least two weeks prior to planned start of domiciling and has had no close contacts with known active sars-cov-2 infection in that time period. * is male or female, from 18 years to 54 years of age inclusive (parts 1 and 3 \[panels a-d, i\]) or ≥ 55 years of age (part 2 \[panels e-h\]) at the time of signing the informed consent. * male participants are eligible to participate if they agree to the following during the intervention period and for at least 2 months after administration of study intervention: be abstinent from heterosexual intercourse as their preferred and usual lifestyle and agree to remain abstinent or agree to use contraception unless confirmed to be azoospermic (vasectomized or secondary to medical cause). * a female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: is not a woman of childbearing potential (wocbp), or is a wocbp and using an acceptable contraceptive method, or is abstinent from heterosexual intercourse as their preferred and usual lifestyle. a wocbp must have a negative highly sensitive pregnancy test before the first dose of study intervention. if a urine test cannot be confirmed as negative, a serum pregnancy test is required.

inclusion criteria: * is in overall good health based on medical history, physical examination, and vital sign (vs) measurements performed prior to randomization, as assessed by the investigator. * is in overall good health based on laboratory safety tests obtained at the screening visit. * has a body mass index (bmi) ≤30 kg/m2 inclusive (after rounding to the nearest whole number). * parts 1 and 2 (panels a-h) only: has negative testing for severe acute respiratory syndrome coronavirus 2 (sars-cov-2) based on both antibody and reverse transcription polymerase chain reaction (rt-pcr), at screening and upon start of domiciling. * part 3 (panel i) only: has positive serology (antibody) testing for sars-cov-2, also with negative sars cov-2 rt-pcr testing at screening and upon start of domiciling, and without symptoms of respiratory infection for at minimum 3 weeks preceding screening. * has been practicing social distancing for at least two weeks prior to planned start of domiciling and has had no close contacts with known active sars-cov-2 infection in that time period. * is male or female, from 18 years to 54 years of age inclusive (parts 1 and 3 \[panels a-d, i\]) or ≥ 55 years of age (part 2 \[panels e-h\]) at the time of signing the informed consent. * male participants are eligible to participate if they agree to the following during the intervention period and for at least 2 months after administration of study intervention: be abstinent from heterosexual intercourse as their preferred and usual lifestyle and agree to remain abstinent or agree to use contraception unless confirmed to be azoospermic (vasectomized or secondary to medical cause). * a female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: is not a woman of childbearing potential (wocbp), or is a wocbp and using an acceptable contraceptive method, or is abstinent from heterosexual intercourse as their preferred and usual lifestyle. a wocbp must have a negative highly sensitive pregnancy test before the first dose of study intervention. if a urine test cannot be confirmed as negative, a serum pregnancy test is required.

inclusion criteria: - is in overall good health based on medical history, physical examination, and vital sign (vs) measurements performed prior to randomization, as assessed by the investigator. - is in overall good health based on laboratory safety tests obtained at the screening visit. - has a body mass index (bmi) ≤30 kg/m2 inclusive (after rounding to the nearest whole number). - parts 1 and 2 (panels a-h) only: has negative testing for severe acute respiratory syndrome coronavirus 2 (sars-cov-2) based on both antibody and reverse transcription polymerase chain reaction (rt-pcr), at screening and upon start of domiciling. - part 3 (panel i) only: has positive serology (antibody) testing for sars-cov-2, also with negative sars cov-2 rt-pcr testing at screening and upon start of domiciling, and without symptoms of respiratory infection for at minimum 3 weeks preceding screening. - has been practicing social distancing for at least two weeks prior to planned start of domiciling and has had no close contacts with known active sars-cov-2 infection in that time period. - is male or female, from 18 years to 54 years of age inclusive (parts 1 and 3 [panels a-d, i]) or ≥ 55 years of age (part 2 [panels e-h]) at the time of signing the informed consent. - male participants are eligible to participate if they agree to the following during the intervention period and for at least 2 months after administration of study intervention: be abstinent from heterosexual intercourse as their preferred and usual lifestyle and agree to remain abstinent or agree to use contraception unless confirmed to be azoospermic (vasectomized or secondary to medical cause). - a female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: is not a woman of childbearing potential (wocbp), or is a wocbp and using an acceptable contraceptive method, or is abstinent from heterosexual intercourse as their preferred and usual lifestyle. a wocbp must have a negative highly sensitive pregnancy test before the first dose of study intervention. if a urine test cannot be confirmed as negative, a serum pregnancy test is required.

inclusion criteria: - is in overall good health based on medical history, physical examination, and vital sign (vs) measurements performed prior to randomization, as assessed by the investigator. - is in overall good health based on laboratory safety tests obtained at the screening visit. - has a body mass index (bmi) ≤30 kg/m2 inclusive (after rounding to the nearest whole number). - parts 1 and 2 (panels a-h) only: has negative testing for severe acute respiratory syndrome coronavirus 2 (sars-cov-2) based on both antibody and reverse transcription polymerase chain reaction (rt-pcr), at screening and upon start of domiciling. - part 3 (panel i) only: has positive serology (antibody) testing for sars-cov-2, also with negative sars cov-2 rt-pcr testing at screening and upon start of domiciling, and without symptoms of respiratory infection for at minimum 3 weeks preceding screening. - has been practicing social distancing for at least two weeks prior to planned start of domiciling and has had no close contacts with known active sars-cov-2 infection in that time period. - is male or female, from 18 years to 54 years of age inclusive (parts 1 and 3 [panels a-d, i]) or ≥ 55 years of age (part 2 [panels e-h]) at the time of signing the informed consent. - male participants are eligible to participate if they agree to the following during the intervention period and for at least 2 months after administration of study intervention: be abstinent from heterosexual intercourse as their preferred and usual lifestyle and agree to remain abstinent or agree to use contraception unless confirmed to be azoospermic (vasectomized or secondary to medical cause). - a female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: is not a woman of childbearing potential (wocbp), or is a wocbp and using an acceptable contraceptive method, or is abstinent from heterosexual intercourse as their preferred and usual lifestyle. a wocbp must have a negative highly sensitive pregnancy test before the first dose of study intervention. if a urine test cannot be confirmed as negative, a serum pregnancy test is required.