inclusion criteria: to be included in this study, each individual must satisfy all the following criteria: 1. medically stable adult male or females ≥ 50 to ≤ 80 years of age at screening. 2. participants may have 1 or more chronic medical diagnoses, but should be clinically stable as assessed by: 1. absence of changes in medical therapy in the past 2 months due to treatment failure or toxicity; 2. absence of medical events qualifying as saes within 3 months; and 3. absence of known, current, and life-limiting diagnoses which render survival to completion of the protocol unlikely in the opinion of the investigator. 3. the participant has a body mass index (bmi) of 17 to 40 kg/m2, inclusive, at screening. 4. willing and able to give informed consent prior to study enrollment. 5. able to attend study visits, comply with study requirements, and provide reliable and complete reports of aes. 6. participants must have completed a primary vaccination series against sars-cov-2 with an authorized covid 19 vaccine (and fulfill national recommendations for his/her age and morbidity category) with receipt of second/last dose of authorized vaccine (with or without boosters\[s\]) ≥ 8 weeks prior to enrollment (first study vaccination). 7. women of childbearing potential (defined as any female participant who is not surgically sterile \[ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy\] or postmenopausal \[defined as amenorrhea at least 12 consecutive months\]) must agree to be heterosexually inactive from at least 28 days prior to enrollment and through the end of the study or agree to consistently use a medically acceptable method of contraception listed below from at least 28 days prior to enrollment and through the end of the study 1. condoms (male or female) with spermicide (if acceptable in country) 2. diaphragm with spermicide 3. cervical cap with spermicide 4. intrauterine device 5. oral or patch contraceptives 6. norplant®, depo-provera®, or other in-country regulatory approved contraceptive method that is designed to protect against pregnancy 7. abstinence, as a form of contraception, is acceptable if in line with the participant's lifestyle 8. participants must be healthy and medically stable, as determined by the investigator (based on review of health status, vital signs \[to include body temperature\], medical history, and targeted physical examination \[to include body weight\]). vital signs must be within medically acceptable ranges prior to vaccination. 9. participants must agree to not participate in any other sars-cov-2 or influenza prevention or treatment studies for the duration of the study. note: for participants who become hospitalized with covid-19, participation in investigational treatment studies is permitted.

inclusion criteria: to be included in this study, each individual must satisfy all the following criteria: 1. medically stable adult male or females ≥ 50 to ≤ 80 years of age at screening. 2. participants may have 1 or more chronic medical diagnoses, but should be clinically stable as assessed by: 1. absence of changes in medical therapy in the past 2 months due to treatment failure or toxicity; 2. absence of medical events qualifying as saes within 3 months; and 3. absence of known, current, and life-limiting diagnoses which render survival to completion of the protocol unlikely in the opinion of the investigator. 3. the participant has a body mass index (bmi) of 17 to 40 kg/m2, inclusive, at screening. 4. willing and able to give informed consent prior to study enrollment. 5. able to attend study visits, comply with study requirements, and provide reliable and complete reports of aes. 6. participants must have completed a primary vaccination series against sars-cov-2 with an authorized covid 19 vaccine (and fulfill national recommendations for his/her age and morbidity category) with receipt of second/last dose of authorized vaccine (with or without boosters\[s\]) ≥ 8 weeks prior to enrollment (first study vaccination). 7. women of childbearing potential (defined as any female participant who is not surgically sterile \[ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy\] or postmenopausal \[defined as amenorrhea at least 12 consecutive months\]) must agree to be heterosexually inactive from at least 28 days prior to enrollment and through the end of the study or agree to consistently use a medically acceptable method of contraception listed below from at least 28 days prior to enrollment and through the end of the study 1. condoms (male or female) with spermicide (if acceptable in country) 2. diaphragm with spermicide 3. cervical cap with spermicide 4. intrauterine device 5. oral or patch contraceptives 6. norplant®, depo-provera®, or other in-country regulatory approved contraceptive method that is designed to protect against pregnancy 7. abstinence, as a form of contraception, is acceptable if in line with the participant's lifestyle 8. participants must be healthy and medically stable, as determined by the investigator (based on review of health status, vital signs \[to include body temperature\], medical history, and targeted physical examination \[to include body weight\]). vital signs must be within medically acceptable ranges prior to vaccination. 9. participants must agree to not participate in any other sars-cov-2 or influenza prevention or treatment studies for the duration of the study. note: for participants who become hospitalized with covid-19, participation in investigational treatment studies is permitted.

inclusion criteria: to be included in this study, each individual must satisfy all the following criteria: medically stable adult male or females ≥ 50 to ≤ 80 years of age at screening. participants may have 1 or more chronic medical diagnoses, but should be clinically stable as assessed by: absence of changes in medical therapy in the past 2 months due to treatment failure or toxicity; absence of medical events qualifying as saes within 3 months; and absence of known, current, and life-limiting diagnoses which render survival to completion of the protocol unlikely in the opinion of the investigator. the participant has a body mass index (bmi) of 17 to 40 kg/m2, inclusive, at screening. willing and able to give informed consent prior to study enrollment. able to attend study visits, comply with study requirements, and provide reliable and complete reports of aes. participants must have completed a primary vaccination series against sars-cov-2 with an authorized covid 19 vaccine (and fulfill national recommendations for his/her age and morbidity category) with receipt of second/last dose of authorized vaccine (with or without boosters[s]) ≥ 8 weeks prior to enrollment (first study vaccination). women of childbearing potential (defined as any female participant who is not surgically sterile [ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy] or postmenopausal [defined as amenorrhea at least 12 consecutive months]) must agree to be heterosexually inactive from at least 28 days prior to enrollment and through the end of the study or agree to consistently use a medically acceptable method of contraception listed below from at least 28 days prior to enrollment and through the end of the study condoms (male or female) with spermicide (if acceptable in country) diaphragm with spermicide cervical cap with spermicide intrauterine device oral or patch contraceptives norplant®, depo-provera®, or other in-country regulatory approved contraceptive method that is designed to protect against pregnancy abstinence, as a form of contraception, is acceptable if in line with the participant's lifestyle participants must be healthy and medically stable, as determined by the investigator (based on review of health status, vital signs [to include body temperature], medical history, and targeted physical examination [to include body weight]). vital signs must be within medically acceptable ranges prior to vaccination. participants must agree to not participate in any other sars-cov-2 or influenza prevention or treatment studies for the duration of the study. note: for participants who become hospitalized with covid-19, participation in investigational treatment studies is permitted.

inclusion criteria: to be included in this study, each individual must satisfy all the following criteria: medically stable adult male or females ≥ 50 to ≤ 80 years of age at screening. participants may have 1 or more chronic medical diagnoses, but should be clinically stable as assessed by: absence of changes in medical therapy in the past 2 months due to treatment failure or toxicity; absence of medical events qualifying as saes within 3 months; and absence of known, current, and life-limiting diagnoses which render survival to completion of the protocol unlikely in the opinion of the investigator. the participant has a body mass index (bmi) of 17 to 40 kg/m2, inclusive, at screening. willing and able to give informed consent prior to study enrollment. able to attend study visits, comply with study requirements, and provide reliable and complete reports of aes. participants must have completed a primary vaccination series against sars-cov-2 with an authorized covid 19 vaccine (and fulfill national recommendations for his/her age and morbidity category) with receipt of second/last dose of authorized vaccine (with or without boosters[s]) ≥ 8 weeks prior to enrollment (first study vaccination). women of childbearing potential (defined as any female participant who is not surgically sterile [ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy] or postmenopausal [defined as amenorrhea at least 12 consecutive months]) must agree to be heterosexually inactive from at least 28 days prior to enrollment and through the end of the study or agree to consistently use a medically acceptable method of contraception listed below from at least 28 days prior to enrollment and through the end of the study condoms (male or female) with spermicide (if acceptable in country) diaphragm with spermicide cervical cap with spermicide intrauterine device oral or patch contraceptives norplant®, depo-provera®, or other in-country regulatory approved contraceptive method that is designed to protect against pregnancy abstinence, as a form of contraception, is acceptable if in line with the participant's lifestyle participants must be healthy and medically stable, as determined by the investigator (based on review of health status, vital signs [to include body temperature], medical history, and targeted physical examination [to include body weight]). vital signs must be within medically acceptable ranges prior to vaccination. participants must agree to not participate in any other sars-cov-2 or influenza prevention or treatment studies for the duration of the study. note: for participants who become hospitalized with covid-19, participation in investigational treatment studies is permitted.