inclusion criteria: adults ≥ 18 years of age, inclusive, at screening. willing and able to give informed consent prior to study enrollment and to comply with study procedures. 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 at least 12 consecutive months]) must agree to be heterosexually inactive from at least 28 days prior to enrollment and through 3 months after the last vaccination or agree to consistently use a medically acceptable method of contraception listed below from at least 28 days prior to enrollment and through 3 months after the last vaccination. condoms (male or female) 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 note: periodic abstinence (eg, calendar, ovulation, symptom-thermal, post-ovulation methods) and withdrawal are not acceptable methods of contraception. is 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 as determined by the investigator prior to the first vaccination. agrees to not participate in any other sars-cov-2 prevention or treatment trials for the duration of the study. note: for participants who become hospitalized with covid-19, participation in investigational treatment studies is permitted. has previously received a documented complete two dose series of the bbibp-corv vaccine with the second dose having been given at least 180 days prior to study vaccination.

inclusion criteria: adults ≥ 18 years of age, inclusive, at screening. willing and able to give informed consent prior to study enrollment and to comply with study procedures. 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 at least 12 consecutive months]) must agree to be heterosexually inactive from at least 28 days prior to enrollment and through 3 months after the last vaccination or agree to consistently use a medically acceptable method of contraception listed below from at least 28 days prior to enrollment and through 3 months after the last vaccination. condoms (male or female) 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 note: periodic abstinence (eg, calendar, ovulation, symptom-thermal, post-ovulation methods) and withdrawal are not acceptable methods of contraception. is 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 as determined by the investigator prior to the first vaccination. agrees to not participate in any other sars-cov-2 prevention or treatment trials for the duration of the study. note: for participants who become hospitalized with covid-19, participation in investigational treatment studies is permitted. has previously received a documented complete two dose series of the bbibp-corv vaccine with the second dose having been given at least 180 days prior to study vaccination.