inclusion criteria: to be eligible for this study, participants must meet all of the following inclusion criteria: 1. adults 18 to 64 years of age, inclusive at screening previously vaccinated with a 2-dose schedule of cominarty™ or vaxzevria™. 2. ≥ 3 months (90 days) since receipt of a booster dose of either comirnatytm or spikevaxtm. 3. be in good health as determined by medical history, physical examination, vital signs, and clinical laboratory assessments with no clinically significant abnormalities as judged by the investigator at screening and randomisation. vital signs must be within medically acceptable ranges prior to the first vaccination. 4. participants of childbearing potential (defined as any participant who has experienced menarche and who is not surgically sterile \[ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy\] or postmenopausal \[defined as amenorrhea of at least 12 consecutive months\]) 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: a. condoms (male or female); diaphragm; cervical cap; intrauterine device; oral or patch contraceptives; norplant®, depo-provera®, or another regulatory approved contraceptive method; abstinence, as a form of contraception, is acceptable if in line with the participant's lifestyle. 5. note: periodic abstinence (e.g., calendar, ovulation, symptom-thermal, post- ovulation methods) and withdrawal method (coitus interruptus) are not acceptable forms of contraception. 6. agrees to not participate in any other sars-cov-2 prevention or treatment trials for the duration of the study. 7. willing and able to give informed consent prior to study enrollment and to comply with all study procedures.

inclusion criteria: to be eligible for this study, participants must meet all of the following inclusion criteria: 1. adults 18 to 64 years of age, inclusive at screening previously vaccinated with a 2-dose schedule of cominarty™ or vaxzevria™. 2. ≥ 3 months (90 days) since receipt of a booster dose of either comirnatytm or spikevaxtm. 3. be in good health as determined by medical history, physical examination, vital signs, and clinical laboratory assessments with no clinically significant abnormalities as judged by the investigator at screening and randomisation. vital signs must be within medically acceptable ranges prior to the first vaccination. 4. participants of childbearing potential (defined as any participant who has experienced menarche and who is not surgically sterile \[ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy\] or postmenopausal \[defined as amenorrhea of at least 12 consecutive months\]) 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: a. condoms (male or female); diaphragm; cervical cap; intrauterine device; oral or patch contraceptives; norplant®, depo-provera®, or another regulatory approved contraceptive method; abstinence, as a form of contraception, is acceptable if in line with the participant's lifestyle. 5. note: periodic abstinence (e.g., calendar, ovulation, symptom-thermal, post- ovulation methods) and withdrawal method (coitus interruptus) are not acceptable forms of contraception. 6. agrees to not participate in any other sars-cov-2 prevention or treatment trials for the duration of the study. 7. willing and able to give informed consent prior to study enrollment and to comply with all study procedures.

inclusion criteria: to be eligible for this study, participants must meet all of the following inclusion criteria: adults 18 to 64 years of age, inclusive at screening previously vaccinated with a 2-dose schedule of cominarty™ or vaxzevria™. ≥ 3 months (90 days) since receipt of a booster dose of either comirnatytm or spikevaxtm. be in good health as determined by medical history, physical examination, vital signs, and clinical laboratory assessments with no clinically significant abnormalities as judged by the investigator at screening and randomisation. vital signs must be within medically acceptable ranges prior to the first vaccination. participants of childbearing potential (defined as any participant who has experienced menarche and who is not surgically sterile [ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy] or postmenopausal [defined as amenorrhea of 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: a. condoms (male or female); diaphragm; cervical cap; intrauterine device; oral or patch contraceptives; norplant®, depo-provera®, or another regulatory approved contraceptive method; abstinence, as a form of contraception, is acceptable if in line with the participant's lifestyle. note: periodic abstinence (e.g., calendar, ovulation, symptom-thermal, post- ovulation methods) and withdrawal method (coitus interruptus) are not acceptable forms of contraception. agrees to not participate in any other sars-cov-2 prevention or treatment trials for the duration of the study. willing and able to give informed consent prior to study enrollment and to comply with all study procedures.

inclusion criteria: to be eligible for this study, participants must meet all of the following inclusion criteria: adults 18 to 64 years of age, inclusive at screening previously vaccinated with a 2-dose schedule of cominarty™ or vaxzevria™. ≥ 3 months (90 days) since receipt of a booster dose of either comirnatytm or spikevaxtm. be in good health as determined by medical history, physical examination, vital signs, and clinical laboratory assessments with no clinically significant abnormalities as judged by the investigator at screening and randomisation. vital signs must be within medically acceptable ranges prior to the first vaccination. participants of childbearing potential (defined as any participant who has experienced menarche and who is not surgically sterile [ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy] or postmenopausal [defined as amenorrhea of 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: a. condoms (male or female); diaphragm; cervical cap; intrauterine device; oral or patch contraceptives; norplant®, depo-provera®, or another regulatory approved contraceptive method; abstinence, as a form of contraception, is acceptable if in line with the participant's lifestyle. note: periodic abstinence (e.g., calendar, ovulation, symptom-thermal, post- ovulation methods) and withdrawal method (coitus interruptus) are not acceptable forms of contraception. agrees to not participate in any other sars-cov-2 prevention or treatment trials for the duration of the study. willing and able to give informed consent prior to study enrollment and to comply with all study procedures.

inclusion criteria: to be eligible for this study, participants must meet all of the following inclusion criteria: adults 18 to 70 years of age, inclusive at screening previously vaccinated with a 2-dose schedule of cominarty™ or vaxzevria™. ≥ 3 months (90 days) since receipt of a booster dose of either comirnatytm or spikevaxtm. be in good health as determined by medical history, physical examination, vital signs, and clinical laboratory assessments with no clinically significant abnormalities as judged by the investigator at screening and randomisation. vital signs must be within medically acceptable ranges prior to the first vaccination. participants of childbearing potential (defined as any participant who has experienced menarche and who is not surgically sterile [ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy] or postmenopausal [defined as amenorrhea of 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: a. condoms (male or female); diaphragm; cervical cap; intrauterine device; oral or patch contraceptives; norplant®, depo-provera®, or another regulatory approved contraceptive method; abstinence, as a form of contraception, is acceptable if in line with the participant's lifestyle. note: periodic abstinence (e.g., calendar, ovulation, symptom-thermal, post- ovulation methods) and withdrawal method (coitus interruptus) are not acceptable forms of contraception. agrees to not participate in any other sars-cov-2 prevention or treatment trials for the duration of the study. willing and able to give informed consent prior to study enrollment and to comply with all study procedures.

inclusion criteria: to be eligible for this study, participants must meet all of the following inclusion criteria: adults 18 to 70 years of age, inclusive at screening previously vaccinated with a 2-dose schedule of cominarty™ or vaxzevria™. ≥ 3 months (90 days) since receipt of a booster dose of either comirnatytm or spikevaxtm. be in good health as determined by medical history, physical examination, vital signs, and clinical laboratory assessments with no clinically significant abnormalities as judged by the investigator at screening and randomisation. vital signs must be within medically acceptable ranges prior to the first vaccination. participants of childbearing potential (defined as any participant who has experienced menarche and who is not surgically sterile [ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy] or postmenopausal [defined as amenorrhea of 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: a. condoms (male or female); diaphragm; cervical cap; intrauterine device; oral or patch contraceptives; norplant®, depo-provera®, or another regulatory approved contraceptive method; abstinence, as a form of contraception, is acceptable if in line with the participant's lifestyle. note: periodic abstinence (e.g., calendar, ovulation, symptom-thermal, post- ovulation methods) and withdrawal method (coitus interruptus) are not acceptable forms of contraception. agrees to not participate in any other sars-cov-2 prevention or treatment trials for the duration of the study. willing and able to give informed consent prior to study enrollment and to comply with all study procedures.