inclusion criteria: 1. male or female subject 18-40 years of age 2. be willing and able to provide personally signed informed consent indicating understanding of the purpose, procedures required for the study and potential risks and benefits of the study, and be willing to participate in the study 3. healthy participants with no chronic medical conditions at study enrollment and during the 6 months before enrollment. participants with history of asymptomatic sars-cov-2 infection who tested positive by pcr or rapid antigen test or participants with history of having signs and symptoms mild covid-19 illness (e.g., fever, cough, sore throat, malaise, headache, muscle pain, nausea, vomiting, diarrhea, loss of taste and smell) but who did not have shortness of breath, dyspnea, or abnormal chest imaging are eligible for the study if they fully recovered a minimum of 6 months before enrollment. 4. meets reproductive inclusion criteria female participant is eligible if she is not pregnant or breastfeeding, and at least 1 of the following conditions applies: • is of childbearing potential and must have a negative pregnancy test prior to study vaccinations and agree to use an effective method of birth control as deemed appropriate by the investigator (e.g., hormonal contraceptive, barrier contraceptive with additional spermicide, or an intrauterine device) beginning \>30 days prior to the first study vaccine administration and continuing for a minimum of 30 days after the last dose of study vaccine. or • is not of childbearing potential, defined as postmenopausal (a minimum of 12 months with no menses without an alternative medical cause) or surgically sterile (bilateral tubal ligation, bilateral oophorectomy or hysterectomy). male participant is eligible to participate if he agrees to the following requirements from the time of first study vaccination until at least 30 days after the last dose of study vaccine: * be abstinent from heterosexual intercourse with a female of childbearing potential or * must agree to use a male condom. in addition to male condom use, an effective method of contraception may be considered in female partners of male participants and * must refrain from sperm donation 5. have previously received 2 or more doses of a licensed covid-19 vaccine(s) with the last dose administered a minimum of 6 months (24 weeks) prior to enrollment. participants vaccinated with any of the vaccines approved by health canada for active immunization to prevent coronavirus disease 2019 (covid-19) caused by severe acute respiratory syndrome coronavirus 2 (sars- cov-2) in individuals 18 years of age and older are eligible for the study. this includes the following covid-19 vaccines: moderna spikevax®, pfizer-biontech comirnaty®, astrazeneca vaxzevria®, janssen jcovden® (johnson \& johnson), novavax nuvaxovid® and medicago covifenz®. participants who received one or more doses of vbi-2902a, vbi-2905a or any other covid-19 vaccines that are either investigational or not approved by health canada are not eligible for the study.

inclusion criteria: 1. male or female subject 18-40 years of age 2. be willing and able to provide personally signed informed consent indicating understanding of the purpose, procedures required for the study and potential risks and benefits of the study, and be willing to participate in the study 3. healthy participants with no chronic medical conditions at study enrollment and during the 6 months before enrollment. participants with history of asymptomatic sars-cov-2 infection who tested positive by pcr or rapid antigen test or participants with history of having signs and symptoms mild covid-19 illness (e.g., fever, cough, sore throat, malaise, headache, muscle pain, nausea, vomiting, diarrhea, loss of taste and smell) but who did not have shortness of breath, dyspnea, or abnormal chest imaging are eligible for the study if they fully recovered a minimum of 6 months before enrollment. 4. meets reproductive inclusion criteria female participant is eligible if she is not pregnant or breastfeeding, and at least 1 of the following conditions applies: • is of childbearing potential and must have a negative pregnancy test prior to study vaccinations and agree to use an effective method of birth control as deemed appropriate by the investigator (e.g., hormonal contraceptive, barrier contraceptive with additional spermicide, or an intrauterine device) beginning \>30 days prior to the first study vaccine administration and continuing for a minimum of 30 days after the last dose of study vaccine. or • is not of childbearing potential, defined as postmenopausal (a minimum of 12 months with no menses without an alternative medical cause) or surgically sterile (bilateral tubal ligation, bilateral oophorectomy or hysterectomy). male participant is eligible to participate if he agrees to the following requirements from the time of first study vaccination until at least 30 days after the last dose of study vaccine: * be abstinent from heterosexual intercourse with a female of childbearing potential or * must agree to use a male condom. in addition to male condom use, an effective method of contraception may be considered in female partners of male participants and * must refrain from sperm donation 5. have previously received 2 or more doses of a licensed covid-19 vaccine(s) with the last dose administered a minimum of 6 months (24 weeks) prior to enrollment. participants vaccinated with any of the vaccines approved by health canada for active immunization to prevent coronavirus disease 2019 (covid-19) caused by severe acute respiratory syndrome coronavirus 2 (sars- cov-2) in individuals 18 years of age and older are eligible for the study. this includes the following covid-19 vaccines: moderna spikevax®, pfizer-biontech comirnaty®, astrazeneca vaxzevria®, janssen jcovden® (johnson \& johnson), novavax nuvaxovid® and medicago covifenz®. participants who received one or more doses of vbi-2902a, vbi-2905a or any other covid-19 vaccines that are either investigational or not approved by health canada are not eligible for the study.

inclusion criteria: male or female subject 18-40 years of age be willing and able to provide personally signed informed consent indicating understanding of the purpose, procedures required for the study and potential risks and benefits of the study, and be willing to participate in the study healthy participants with no chronic medical conditions at study enrollment and during the 6 months before enrollment. participants with history of asymptomatic sars-cov-2 infection who tested positive by pcr or rapid antigen test or participants with history of having signs and symptoms mild covid-19 illness (e.g., fever, cough, sore throat, malaise, headache, muscle pain, nausea, vomiting, diarrhea, loss of taste and smell) but who did not have shortness of breath, dyspnea, or abnormal chest imaging are eligible for the study if they fully recovered a minimum of 6 months before enrollment. meets reproductive inclusion criteria female participant is eligible if she is not pregnant or breastfeeding, and at least 1 of the following conditions applies: • is of childbearing potential and must have a negative pregnancy test prior to study vaccinations and agree to use an effective method of birth control as deemed appropriate by the investigator (e.g., hormonal contraceptive, barrier contraceptive with additional spermicide, or an intrauterine device) beginning >30 days prior to the first study vaccine administration and continuing for a minimum of 30 days after the last dose of study vaccine. or • is not of childbearing potential, defined as postmenopausal (a minimum of 12 months with no menses without an alternative medical cause) or surgically sterile (bilateral tubal ligation, bilateral oophorectomy or hysterectomy). male participant is eligible to participate if he agrees to the following requirements from the time of first study vaccination until at least 30 days after the last dose of study vaccine: be abstinent from heterosexual intercourse with a female of childbearing potential or must agree to use a male condom. in addition to male condom use, an effective method of contraception may be considered in female partners of male participants and must refrain from sperm donation have previously received 2 or more doses of a licensed covid-19 vaccine(s) with the last dose administered a minimum of 6 months (24 weeks) prior to enrollment. participants vaccinated with any of the vaccines approved by health canada for active immunization to prevent coronavirus disease 2019 (covid-19) caused by severe acute respiratory syndrome coronavirus 2 (sars- cov-2) in individuals 18 years of age and older are eligible for the study. this includes the following covid-19 vaccines: moderna spikevax®, pfizer-biontech comirnaty®, astrazeneca vaxzevria®, janssen jcovden® (johnson & johnson), novavax nuvaxovid® and medicago covifenz®. participants who received one or more doses of vbi-2902a, vbi-2905a or any other covid-19 vaccines that are either investigational or not approved by health canada are not eligible for the study.

inclusion criteria: male or female subject 18-40 years of age be willing and able to provide personally signed informed consent indicating understanding of the purpose, procedures required for the study and potential risks and benefits of the study, and be willing to participate in the study healthy participants with no chronic medical conditions at study enrollment and during the 6 months before enrollment. participants with history of asymptomatic sars-cov-2 infection who tested positive by pcr or rapid antigen test or participants with history of having signs and symptoms mild covid-19 illness (e.g., fever, cough, sore throat, malaise, headache, muscle pain, nausea, vomiting, diarrhea, loss of taste and smell) but who did not have shortness of breath, dyspnea, or abnormal chest imaging are eligible for the study if they fully recovered a minimum of 6 months before enrollment. meets reproductive inclusion criteria female participant is eligible if she is not pregnant or breastfeeding, and at least 1 of the following conditions applies: • is of childbearing potential and must have a negative pregnancy test prior to study vaccinations and agree to use an effective method of birth control as deemed appropriate by the investigator (e.g., hormonal contraceptive, barrier contraceptive with additional spermicide, or an intrauterine device) beginning >30 days prior to the first study vaccine administration and continuing for a minimum of 30 days after the last dose of study vaccine. or • is not of childbearing potential, defined as postmenopausal (a minimum of 12 months with no menses without an alternative medical cause) or surgically sterile (bilateral tubal ligation, bilateral oophorectomy or hysterectomy). male participant is eligible to participate if he agrees to the following requirements from the time of first study vaccination until at least 30 days after the last dose of study vaccine: be abstinent from heterosexual intercourse with a female of childbearing potential or must agree to use a male condom. in addition to male condom use, an effective method of contraception may be considered in female partners of male participants and must refrain from sperm donation have previously received 2 or more doses of a licensed covid-19 vaccine(s) with the last dose administered a minimum of 6 months (24 weeks) prior to enrollment. participants vaccinated with any of the vaccines approved by health canada for active immunization to prevent coronavirus disease 2019 (covid-19) caused by severe acute respiratory syndrome coronavirus 2 (sars- cov-2) in individuals 18 years of age and older are eligible for the study. this includes the following covid-19 vaccines: moderna spikevax®, pfizer-biontech comirnaty®, astrazeneca vaxzevria®, janssen jcovden® (johnson & johnson), novavax nuvaxovid® and medicago covifenz®. participants who received one or more doses of vbi-2902a, vbi-2905a or any other covid-19 vaccines that are either investigational or not approved by health canada are not eligible for the study.