inclusion criteria: 1. able to understand and comply with the study procedures, understand the risks involved in the study, and provide written informed consent before the first study-specific procedure; 2. healthy volunteers aged above 18 years at time of screening; 3. have received last covid-19 vaccination more than 3 months ago (more than 90 days) \[only step 1\] 4. have had at least authorised primary covid-19 vaccination(s) regardless of numbers of booster. \[only step 2\] 5. the last authorised covid-19 vaccination, the participants received, should be more than 4 months (16 weeks) prior to the first eg-covid or eg-covaro vaccination. \[only step 2\] 6. participants must have a body mass index (bmi) between ≥18.5 and ≤30.0 kg/m2 at screening; 7. availability to volunteer for the entire study duration and be willing to adhere to all protocol requirements; 8. must have a negative urine pregnancy test on the day of dosing prior to each vaccination; 9. must agree not to donate blood or receive transfusion (including whole blood, plasma, and platelet components). 10. must agree to use highly effective, medically accepted double-barrier contraception (both male and female partners) from screening until study completion (until 3 months after second vaccination) as specified below in this criterion. highly effective double-barrier contraception is defined as use of a condom and one of the following: 1. birth control pills (the pill) 2. depot or injectable birth control 3. iud (intrauterine device) 4. birth control patch (e.g., ortho evra) 5. nuvaring® 6. implantable contraception (e.g., implanon) 7. documented evidence of surgical sterilisation at least 6 months prior to screening, i.e., tubal ligation for female or vasectomy for male rhythm methods are not considered as highly effective methods of birth control. female participants and female partners of male participants must use contraception from the time of informed consent and for 90 days after last vaccination of study drug. female not of childbearing potential must be postmenopausal for ≥12 months. postmenopausal status will be confirmed through testing of follicle stimulating hormone (fsh) levels ≥ 40 iu/ml at screening for amenorrhoeic female participants. male participants must refrain from sperm donation from start of study and for 90 days after the last vaccination of study drug. female participants who has had hysterectomy at least 6 months prior to screening must provide documented evidence of surgical sterilisation and are not required to use double barrier contraception where this is the usual and preferred lifestyle. participants who are in same-sex relationships are not required to use contraception. abstinence is acceptable where this is the usual and preferred lifestyle.

inclusion criteria: 1. able to understand and comply with the study procedures, understand the risks involved in the study, and provide written informed consent before the first study-specific procedure; 2. healthy volunteers aged above 18 years at time of screening; 3. have received last covid-19 vaccination more than 3 months ago (more than 90 days) \[only step 1\] 4. have had at least authorised primary covid-19 vaccination(s) regardless of numbers of booster. \[only step 2\] 5. the last authorised covid-19 vaccination, the participants received, should be more than 4 months (16 weeks) prior to the first eg-covid or eg-covaro vaccination. \[only step 2\] 6. participants must have a body mass index (bmi) between ≥18.5 and ≤30.0 kg/m2 at screening; 7. availability to volunteer for the entire study duration and be willing to adhere to all protocol requirements; 8. must have a negative urine pregnancy test on the day of dosing prior to each vaccination; 9. must agree not to donate blood or receive transfusion (including whole blood, plasma, and platelet components). 10. must agree to use highly effective, medically accepted double-barrier contraception (both male and female partners) from screening until study completion (until 3 months after second vaccination) as specified below in this criterion. highly effective double-barrier contraception is defined as use of a condom and one of the following: 1. birth control pills (the pill) 2. depot or injectable birth control 3. iud (intrauterine device) 4. birth control patch (e.g., ortho evra) 5. nuvaring® 6. implantable contraception (e.g., implanon) 7. documented evidence of surgical sterilisation at least 6 months prior to screening, i.e., tubal ligation for female or vasectomy for male rhythm methods are not considered as highly effective methods of birth control. female participants and female partners of male participants must use contraception from the time of informed consent and for 90 days after last vaccination of study drug. female not of childbearing potential must be postmenopausal for ≥12 months. postmenopausal status will be confirmed through testing of follicle stimulating hormone (fsh) levels ≥ 40 iu/ml at screening for amenorrhoeic female participants. male participants must refrain from sperm donation from start of study and for 90 days after the last vaccination of study drug. female participants who has had hysterectomy at least 6 months prior to screening must provide documented evidence of surgical sterilisation and are not required to use double barrier contraception where this is the usual and preferred lifestyle. participants who are in same-sex relationships are not required to use contraception. abstinence is acceptable where this is the usual and preferred lifestyle.

inclusion criteria: able to understand and comply with the study procedures, understand the risks involved in the study, and provide written informed consent before the first study-specific procedure; healthy volunteers aged above 18 years at time of screening; have received last covid-19 vaccination more than 3 months ago (more than 90 days) [only step 1] have had at least authorised primary covid-19 vaccination(s) regardless of numbers of booster. [only step 2] the last authorised covid-19 vaccination, the participants received, should be more than 4 months (16 weeks) prior to the first eg-covid or eg-covaro vaccination. [only step 2] participants must have a body mass index (bmi) between ≥18.5 and ≤30.0 kg/m2 at screening; availability to volunteer for the entire study duration and be willing to adhere to all protocol requirements; must have a negative urine pregnancy test on the day of dosing prior to each vaccination; must agree not to donate blood or receive transfusion (including whole blood, plasma, and platelet components). must agree to use highly effective, medically accepted double-barrier contraception (both male and female partners) from screening until study completion (until 3 months after second vaccination) as specified below in this criterion. highly effective double-barrier contraception is defined as use of a condom and one of the following: birth control pills (the pill) depot or injectable birth control iud (intrauterine device) birth control patch (e.g., ortho evra) nuvaring® implantable contraception (e.g., implanon) documented evidence of surgical sterilisation at least 6 months prior to screening, i.e., tubal ligation for female or vasectomy for male rhythm methods are not considered as highly effective methods of birth control. female participants and female partners of male participants must use contraception from the time of informed consent and for 90 days after last vaccination of study drug. female not of childbearing potential must be postmenopausal for ≥12 months. postmenopausal status will be confirmed through testing of follicle stimulating hormone (fsh) levels ≥ 40 iu/ml at screening for amenorrhoeic female participants. male participants must refrain from sperm donation from start of study and for 90 days after the last vaccination of study drug. female participants who has had hysterectomy at least 6 months prior to screening must provide documented evidence of surgical sterilisation and are not required to use double barrier contraception where this is the usual and preferred lifestyle. participants who are in same-sex relationships are not required to use contraception. abstinence is acceptable where this is the usual and preferred lifestyle.

inclusion criteria: able to understand and comply with the study procedures, understand the risks involved in the study, and provide written informed consent before the first study-specific procedure; healthy volunteers aged above 18 years at time of screening; have received last covid-19 vaccination more than 3 months ago (more than 90 days) [only step 1] have had at least authorised primary covid-19 vaccination(s) regardless of numbers of booster. [only step 2] the last authorised covid-19 vaccination, the participants received, should be more than 4 months (16 weeks) prior to the first eg-covid or eg-covaro vaccination. [only step 2] participants must have a body mass index (bmi) between ≥18.5 and ≤30.0 kg/m2 at screening; availability to volunteer for the entire study duration and be willing to adhere to all protocol requirements; must have a negative urine pregnancy test on the day of dosing prior to each vaccination; must agree not to donate blood or receive transfusion (including whole blood, plasma, and platelet components). must agree to use highly effective, medically accepted double-barrier contraception (both male and female partners) from screening until study completion (until 3 months after second vaccination) as specified below in this criterion. highly effective double-barrier contraception is defined as use of a condom and one of the following: birth control pills (the pill) depot or injectable birth control iud (intrauterine device) birth control patch (e.g., ortho evra) nuvaring® implantable contraception (e.g., implanon) documented evidence of surgical sterilisation at least 6 months prior to screening, i.e., tubal ligation for female or vasectomy for male rhythm methods are not considered as highly effective methods of birth control. female participants and female partners of male participants must use contraception from the time of informed consent and for 90 days after last vaccination of study drug. female not of childbearing potential must be postmenopausal for ≥12 months. postmenopausal status will be confirmed through testing of follicle stimulating hormone (fsh) levels ≥ 40 iu/ml at screening for amenorrhoeic female participants. male participants must refrain from sperm donation from start of study and for 90 days after the last vaccination of study drug. female participants who has had hysterectomy at least 6 months prior to screening must provide documented evidence of surgical sterilisation and are not required to use double barrier contraception where this is the usual and preferred lifestyle. participants who are in same-sex relationships are not required to use contraception. abstinence is acceptable where this is the usual and preferred lifestyle.

inclusion criteria: able to understand and comply with the study procedures, understand the risks involved in the study, and provide written informed consent before the first study-specific procedure; healthy volunteers aged above 18 years at time of screening; have received last covid-19 vaccination more than 3 months ago (more than 90 days) [only step 1] participants must have a body mass index (bmi) between ≥18.5 and ≤30.0 kg/m2 at screening; availability to volunteer for the entire study duration and be willing to adhere to all protocol requirements; must have a negative urine pregnancy test on the day of dosing prior to each vaccination; must agree not to donate blood or receive transfusion (including whole blood, plasma, and platelet components). must agree to use highly effective, medically accepted double-barrier contraception (both male and female partners) from screening until study completion (until 3 months after second vaccination) as specified below in this criterion. highly effective double-barrier contraception is defined as use of a condom and one of the following: birth control pills (the pill) depot or injectable birth control iud (intrauterine device) birth control patch (e.g., ortho evra) nuvaring® implantable contraception (e.g., implanon) documented evidence of surgical sterilisation at least 6 months prior to screening, i.e., tubal ligation for female or vasectomy for male rhythm methods are not considered as highly effective methods of birth control. female participants and female partners of male participants must use contraception from the time of informed consent and for 90 days after last vaccination of study drug. female not of childbearing potential must be postmenopausal for ≥12 months. postmenopausal status will be confirmed through testing of follicle stimulating hormone (fsh) levels ≥ 40 iu/ml at screening for amenorrhoeic female participants. male participants must refrain from sperm donation from start of study and for 90 days after the last vaccination of study drug. female participants who has had hysterectomy at least 6 months prior to screening must provide documented evidence of surgical sterilisation and are not required to use double barrier contraception where this is the usual and preferred lifestyle. participants who are in same-sex relationships are not required to use contraception. abstinence is acceptable where this is the usual and preferred lifestyle.

inclusion criteria: able to understand and comply with the study procedures, understand the risks involved in the study, and provide written informed consent before the first study-specific procedure; healthy volunteers aged above 18 years at time of screening; have received last covid-19 vaccination more than 3 months ago (more than 90 days) [only step 1] participants must have a body mass index (bmi) between ≥18.5 and ≤30.0 kg/m2 at screening; availability to volunteer for the entire study duration and be willing to adhere to all protocol requirements; must have a negative urine pregnancy test on the day of dosing prior to each vaccination; must agree not to donate blood or receive transfusion (including whole blood, plasma, and platelet components). must agree to use highly effective, medically accepted double-barrier contraception (both male and female partners) from screening until study completion (until 3 months after second vaccination) as specified below in this criterion. highly effective double-barrier contraception is defined as use of a condom and one of the following: birth control pills (the pill) depot or injectable birth control iud (intrauterine device) birth control patch (e.g., ortho evra) nuvaring® implantable contraception (e.g., implanon) documented evidence of surgical sterilisation at least 6 months prior to screening, i.e., tubal ligation for female or vasectomy for male rhythm methods are not considered as highly effective methods of birth control. female participants and female partners of male participants must use contraception from the time of informed consent and for 90 days after last vaccination of study drug. female not of childbearing potential must be postmenopausal for ≥12 months. postmenopausal status will be confirmed through testing of follicle stimulating hormone (fsh) levels ≥ 40 iu/ml at screening for amenorrhoeic female participants. male participants must refrain from sperm donation from start of study and for 90 days after the last vaccination of study drug. female participants who has had hysterectomy at least 6 months prior to screening must provide documented evidence of surgical sterilisation and are not required to use double barrier contraception where this is the usual and preferred lifestyle. participants who are in same-sex relationships are not required to use contraception. abstinence is acceptable where this is the usual and preferred lifestyle.