adult and adolescent participants meeting any of the following criteria will be excluded from the study: 1. unstable acute or chronic illness. criteria for unstable medical conditions include: 1. substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. 2. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. note: well-controlled human immunodeficiency virus \[hiv\] with undetectable hiv rna \[\< 50 copies/ml\] and cd4 count \> 200 cells/µl for at least 1 year, documented within the last 6 months, is not considered an unstable chronic illness. participant's or parent's/caregiver's verbal report will suffice as documentation. 2. participation in research involving an investigational product (drug/biologic/device) administered within 45 days prior to first study vaccination. 3. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. a previous diagnosis of covid-19 during participation in this trial is not exclusionary for the booster amendment. 4. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (i.e., 28 days after second vaccination), except for influenza vaccination, which may be received ≥ 4 days prior to or ≥ 7 days after either study vaccination. rabies vaccine, at any time it is medically indicated, is not exclusionary. prior receipt of another approved or authorized covid-19 vaccine prior to booster injection is not exclusionary in the booster amendment. such participants must provide documentation of vaccine and date(s) of administration. 5. autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) or therapy that causes clinically significant immunosuppression. note: stable endocrine disorders (eg, thyroiditis, pancreatitis, including stable diabetes mellitus) are not excluded. 6. chronic administration (defined as \> 14 continuous days) of immunosuppressant or systemic glucocorticoids causing clinically significant immunocompromise, within 90 days prior to first study vaccination and/or third (booster) vaccination. note: an immunosuppressant dose of glucocorticoid is defined as a systemic dose ≥ 20 mg of prednisone per day or equivalent. the use of topical, inhaled, and nasal glucocorticoids is permitted. topical tacrolimus and ocular cyclosporin are permitted. 7. received immunoglobulin or blood-derived products, within 90 days prior to first study vaccination and/or third (booster) vaccination. 8. active cancer (malignancy) on chemotherapy that is judged to cause clinically significant immunocompromise within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). this criterion is not applicable to participants diagnosed during participation in this trial who accept participation in the booster amendment. 9. any known allergies to products contained in the investigational product. 10. participants who are breastfeeding, pregnant, or who plan to become pregnant within 3 months following last study vaccination. 11. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. 12. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). 13. current participation in any other covid-19 prevention clinical trial. 14. adult participants who have not received a full dose of any authorized/approved covid-19 vaccine and are unable to provide valid documentation of vaccination will be excluded from the booster amendment. adult and adolescent participants meeting any of the following criteria will be excluded from the substudy: 1. history of laboratory-confirmed (by pcr or other antigen testing) covid-19 infection ≤ 4 months prior to entering the substudy. 2. known to be clinically significantly immunocompromised. 3. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to entering substudy. 4. participants who are breastfeeding, pregnant, or who plan to become pregnant prior to the end of substudy. 5. history of confirmed myocarditis and/or pericarditis since enrollment to the parent study. 6. any condition that, in the opinion of the investigator, might pose a health risk to the participant, interfere with protocol compliance or interfere with evaluation of the trial vaccine. 7. study team member or immediate family member of any study team member (inclusive of sponsor, cro, and study site personnel involved in the conduct or planning of the substudy).

adult and adolescent participants meeting any of the following criteria will be excluded from the study: 1. unstable acute or chronic illness. criteria for unstable medical conditions include: 1. substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. 2. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. note: well-controlled human immunodeficiency virus \[hiv\] with undetectable hiv rna \[\< 50 copies/ml\] and cd4 count \> 200 cells/µl for at least 1 year, documented within the last 6 months, is not considered an unstable chronic illness. participant's or parent's/caregiver's verbal report will suffice as documentation. 2. participation in research involving an investigational product (drug/biologic/device) administered within 45 days prior to first study vaccination. 3. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. a previous diagnosis of covid-19 during participation in this trial is not exclusionary for the booster amendment. 4. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (i.e., 28 days after second vaccination), except for influenza vaccination, which may be received ≥ 4 days prior to or ≥ 7 days after either study vaccination. rabies vaccine, at any time it is medically indicated, is not exclusionary. prior receipt of another approved or authorized covid-19 vaccine prior to booster injection is not exclusionary in the booster amendment. such participants must provide documentation of vaccine and date(s) of administration. 5. autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) or therapy that causes clinically significant immunosuppression. note: stable endocrine disorders (eg, thyroiditis, pancreatitis, including stable diabetes mellitus) are not excluded. 6. chronic administration (defined as \> 14 continuous days) of immunosuppressant or systemic glucocorticoids causing clinically significant immunocompromise, within 90 days prior to first study vaccination and/or third (booster) vaccination. note: an immunosuppressant dose of glucocorticoid is defined as a systemic dose ≥ 20 mg of prednisone per day or equivalent. the use of topical, inhaled, and nasal glucocorticoids is permitted. topical tacrolimus and ocular cyclosporin are permitted. 7. received immunoglobulin or blood-derived products, within 90 days prior to first study vaccination and/or third (booster) vaccination. 8. active cancer (malignancy) on chemotherapy that is judged to cause clinically significant immunocompromise within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). this criterion is not applicable to participants diagnosed during participation in this trial who accept participation in the booster amendment. 9. any known allergies to products contained in the investigational product. 10. participants who are breastfeeding, pregnant, or who plan to become pregnant within 3 months following last study vaccination. 11. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. 12. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). 13. current participation in any other covid-19 prevention clinical trial. 14. adult participants who have not received a full dose of any authorized/approved covid-19 vaccine and are unable to provide valid documentation of vaccination will be excluded from the booster amendment. adult and adolescent participants meeting any of the following criteria will be excluded from the substudy: 1. history of laboratory-confirmed (by pcr or other antigen testing) covid-19 infection ≤ 4 months prior to entering the substudy. 2. known to be clinically significantly immunocompromised. 3. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to entering substudy. 4. participants who are breastfeeding, pregnant, or who plan to become pregnant prior to the end of substudy. 5. history of confirmed myocarditis and/or pericarditis since enrollment to the parent study. 6. any condition that, in the opinion of the investigator, might pose a health risk to the participant, interfere with protocol compliance or interfere with evaluation of the trial vaccine. 7. study team member or immediate family member of any study team member (inclusive of sponsor, cro, and study site personnel involved in the conduct or planning of the substudy).

adult and adolescent participants meeting any of the following criteria will be excluded from the study: unstable acute or chronic illness. criteria for unstable medical conditions include: substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. note: well-controlled human immunodeficiency virus [hiv] with undetectable hiv rna [< 50 copies/ml] and cd4 count > 200 cells/µl for at least 1 year, documented within the last 6 months, is not considered an unstable chronic illness. participant's or parent's/caregiver's verbal report will suffice as documentation. participation in research involving an investigational product (drug/biologic/device) administered within 45 days prior to first study vaccination. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. a previous diagnosis of covid-19 during participation in this trial is not exclusionary for the booster amendment. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (i.e., 28 days after second vaccination), except for influenza vaccination, which may be received ≥ 4 days prior to or ≥ 7 days after either study vaccination. rabies vaccine, at any time it is medically indicated, is not exclusionary. prior receipt of another approved or authorized covid-19 vaccine prior to booster injection is not exclusionary in the booster amendment. such participants must provide documentation of vaccine and date(s) of administration. autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) or therapy that causes clinically significant immunosuppression. note: stable endocrine disorders (eg, thyroiditis, pancreatitis, including stable diabetes mellitus) are not excluded. chronic administration (defined as > 14 continuous days) of immunosuppressant or systemic glucocorticoids causing clinically significant immunocompromise, within 90 days prior to first study vaccination and/or third (booster) vaccination. note: an immunosuppressant dose of glucocorticoid is defined as a systemic dose ≥ 20 mg of prednisone per day or equivalent. the use of topical, inhaled, and nasal glucocorticoids is permitted. topical tacrolimus and ocular cyclosporin are permitted. received immunoglobulin or blood-derived products, within 90 days prior to first study vaccination and/or third (booster) vaccination. active cancer (malignancy) on chemotherapy that is judged to cause clinically significant immunocompromise within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). this criterion is not applicable to participants diagnosed during participation in this trial who accept participation in the booster amendment. any known allergies to products contained in the investigational product. participants who are breastfeeding, pregnant, or who plan to become pregnant within 3 months following last study vaccination. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). current participation in any other covid-19 prevention clinical trial. adult participants who have not received a full dose of any authorized/approved covid-19 vaccine and are unable to provide valid documentation of vaccination will be excluded from the booster amendment. adult and adolescent participants meeting any of the following criteria will be excluded from the substudy: history of laboratory-confirmed (by pcr or other antigen testing) covid-19 infection ≤ 4 months prior to entering the substudy. known to be clinically significantly immunocompromised. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to entering substudy. participants who are breastfeeding, pregnant, or who plan to become pregnant prior to the end of substudy. history of confirmed myocarditis and/or pericarditis since enrollment to the parent study. any condition that, in the opinion of the investigator, might pose a health risk to the participant, interfere with protocol compliance or interfere with evaluation of the trial vaccine. study team member or immediate family member of any study team member (inclusive of sponsor, cro, and study site personnel involved in the conduct or planning of the substudy).

adult and adolescent participants meeting any of the following criteria will be excluded from the study: unstable acute or chronic illness. criteria for unstable medical conditions include: substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. note: well-controlled human immunodeficiency virus [hiv] with undetectable hiv rna [< 50 copies/ml] and cd4 count > 200 cells/µl for at least 1 year, documented within the last 6 months, is not considered an unstable chronic illness. participant's or parent's/caregiver's verbal report will suffice as documentation. participation in research involving an investigational product (drug/biologic/device) administered within 45 days prior to first study vaccination. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. a previous diagnosis of covid-19 during participation in this trial is not exclusionary for the booster amendment. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (i.e., 28 days after second vaccination), except for influenza vaccination, which may be received ≥ 4 days prior to or ≥ 7 days after either study vaccination. rabies vaccine, at any time it is medically indicated, is not exclusionary. prior receipt of another approved or authorized covid-19 vaccine prior to booster injection is not exclusionary in the booster amendment. such participants must provide documentation of vaccine and date(s) of administration. autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) or therapy that causes clinically significant immunosuppression. note: stable endocrine disorders (eg, thyroiditis, pancreatitis, including stable diabetes mellitus) are not excluded. chronic administration (defined as > 14 continuous days) of immunosuppressant or systemic glucocorticoids causing clinically significant immunocompromise, within 90 days prior to first study vaccination and/or third (booster) vaccination. note: an immunosuppressant dose of glucocorticoid is defined as a systemic dose ≥ 20 mg of prednisone per day or equivalent. the use of topical, inhaled, and nasal glucocorticoids is permitted. topical tacrolimus and ocular cyclosporin are permitted. received immunoglobulin or blood-derived products, within 90 days prior to first study vaccination and/or third (booster) vaccination. active cancer (malignancy) on chemotherapy that is judged to cause clinically significant immunocompromise within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). this criterion is not applicable to participants diagnosed during participation in this trial who accept participation in the booster amendment. any known allergies to products contained in the investigational product. participants who are breastfeeding, pregnant, or who plan to become pregnant within 3 months following last study vaccination. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). current participation in any other covid-19 prevention clinical trial. adult participants who have not received a full dose of any authorized/approved covid-19 vaccine and are unable to provide valid documentation of vaccination will be excluded from the booster amendment. adult and adolescent participants meeting any of the following criteria will be excluded from the substudy: history of laboratory-confirmed (by pcr or other antigen testing) covid-19 infection ≤ 4 months prior to entering the substudy. known to be clinically significantly immunocompromised. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to entering substudy. participants who are breastfeeding, pregnant, or who plan to become pregnant prior to the end of substudy. history of confirmed myocarditis and/or pericarditis since enrollment to the parent study. any condition that, in the opinion of the investigator, might pose a health risk to the participant, interfere with protocol compliance or interfere with evaluation of the trial vaccine. study team member or immediate family member of any study team member (inclusive of sponsor, cro, and study site personnel involved in the conduct or planning of the substudy).

adult and pediatric participants meeting any of the following criteria will be excluded from the study: unstable acute or chronic illness. criteria for unstable medical conditions include: substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. note: well-controlled human immunodeficiency virus [hiv] with undetectable hiv rna [< 50 copies/ml] and cd4 count > 200 cells/µl for at least 1 year, documented within the last 6 months, is not considered an unstable chronic illness. participant's or parent's/caregiver's verbal report will suffice as documentation. participation in research involving an investigational product (drug/biologic/device) administered within 45 days prior to first study vaccination. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. a previous diagnosis of covid-19 during participation in this trial is not exclusionary for the booster amendment. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (i.e., 28 days after second vaccination), except for influenza vaccination, which may be received ≥ 4 days prior to or ≥ 7 days after either study vaccination. rabies vaccine, at any time it is medically indicated, is not exclusionary. prior receipt of another approved or authorized covid-19 vaccine prior to booster injection is not exclusionary in the booster amendment. such participants must provide documentation of vaccine and date(s) of administration. autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) or therapy that causes clinically significant immunosuppression. note: stable endocrine disorders (eg, thyroiditis, pancreatitis, including stable diabetes mellitus) are not excluded. chronic administration (defined as > 14 continuous days) of immunosuppressant or systemic glucocorticoids causing clinically significant immunocompromise, within 90 days prior to first study vaccination and/or third (booster) vaccination. note: an immunosuppressant dose of glucocorticoid is defined as a systemic dose ≥ 20 mg of prednisone per day or equivalent. the use of topical, inhaled, and nasal glucocorticoids is permitted. topical tacrolimus and ocular cyclosporin are permitted. received immunoglobulin or blood-derived products, within 90 days prior to first study vaccination and/or third (booster) vaccination. active cancer (malignancy) on chemotherapy that is judged to cause clinically significant immunocompromise within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). this criterion is not applicable to participants diagnosed during participation in this trial who accept participation in the booster amendment. any known allergies to products contained in the investigational product. participants who are breastfeeding, pregnant, or who plan to become pregnant within 3 months following last study vaccination. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). current participation in any other covid-19 prevention clinical trial. adult participants who have not received a full dose of any authorized/approved covid-19 vaccine and are unable to provide valid documentation of vaccination will be excluded from the booster amendment. adult participants meeting any of the following criteria will be excluded from the substudy: history of laboratory-confirmed (by pcr or other antigen testing) covid-19 infection ≤ 4 months prior to entering the substudy. known to be clinically significantly immunocompromised. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to entering substudy. participants who are breastfeeding, pregnant, or who plan to become pregnant prior to the end of substudy. history of confirmed myocarditis and/or pericarditis since enrollment to the parent study. any condition that, in the opinion of the investigator, might pose a health risk to the participant, interfere with protocol compliance or interfere with evaluation of the trial vaccine. study team member or immediate family member of any study team member (inclusive of sponsor, cro, and study site personnel involved in the conduct or planning of the substudy).

adult and pediatric participants meeting any of the following criteria will be excluded from the study: unstable acute or chronic illness. criteria for unstable medical conditions include: substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. note: well-controlled human immunodeficiency virus [hiv] with undetectable hiv rna [< 50 copies/ml] and cd4 count > 200 cells/µl for at least 1 year, documented within the last 6 months, is not considered an unstable chronic illness. participant's or parent's/caregiver's verbal report will suffice as documentation. participation in research involving an investigational product (drug/biologic/device) administered within 45 days prior to first study vaccination. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. a previous diagnosis of covid-19 during participation in this trial is not exclusionary for the booster amendment. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (i.e., 28 days after second vaccination), except for influenza vaccination, which may be received ≥ 4 days prior to or ≥ 7 days after either study vaccination. rabies vaccine, at any time it is medically indicated, is not exclusionary. prior receipt of another approved or authorized covid-19 vaccine prior to booster injection is not exclusionary in the booster amendment. such participants must provide documentation of vaccine and date(s) of administration. autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) or therapy that causes clinically significant immunosuppression. note: stable endocrine disorders (eg, thyroiditis, pancreatitis, including stable diabetes mellitus) are not excluded. chronic administration (defined as > 14 continuous days) of immunosuppressant or systemic glucocorticoids causing clinically significant immunocompromise, within 90 days prior to first study vaccination and/or third (booster) vaccination. note: an immunosuppressant dose of glucocorticoid is defined as a systemic dose ≥ 20 mg of prednisone per day or equivalent. the use of topical, inhaled, and nasal glucocorticoids is permitted. topical tacrolimus and ocular cyclosporin are permitted. received immunoglobulin or blood-derived products, within 90 days prior to first study vaccination and/or third (booster) vaccination. active cancer (malignancy) on chemotherapy that is judged to cause clinically significant immunocompromise within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). this criterion is not applicable to participants diagnosed during participation in this trial who accept participation in the booster amendment. any known allergies to products contained in the investigational product. participants who are breastfeeding, pregnant, or who plan to become pregnant within 3 months following last study vaccination. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). current participation in any other covid-19 prevention clinical trial. adult participants who have not received a full dose of any authorized/approved covid-19 vaccine and are unable to provide valid documentation of vaccination will be excluded from the booster amendment. adult participants meeting any of the following criteria will be excluded from the substudy: history of laboratory-confirmed (by pcr or other antigen testing) covid-19 infection ≤ 4 months prior to entering the substudy. known to be clinically significantly immunocompromised. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to entering substudy. participants who are breastfeeding, pregnant, or who plan to become pregnant prior to the end of substudy. history of confirmed myocarditis and/or pericarditis since enrollment to the parent study. any condition that, in the opinion of the investigator, might pose a health risk to the participant, interfere with protocol compliance or interfere with evaluation of the trial vaccine. study team member or immediate family member of any study team member (inclusive of sponsor, cro, and study site personnel involved in the conduct or planning of the substudy).

adult and pediatric participants meeting any of the following criteria will be excluded from the study: unstable acute or chronic illness. criteria for unstable medical conditions include: substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. note: well-controlled human immunodeficiency virus [hiv] with undetectable hiv rna [< 50 copies/ml] and cd4 count > 200 cells/µl for at least 1 year, documented within the last 6 months, is not considered an unstable chronic illness. participant's or parent's/caregiver's verbal report will suffice as documentation. participation in research involving an investigational product (drug/biologic/device) administered within 45 days prior to first study vaccination. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. a previous diagnosis of covid-19 during participation in this trial is not exclusionary for the booster amendment. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (i.e., 28 days after second vaccination), except for influenza vaccination, which may be received ≥ 4 days prior to or ≥ 7 days after either study vaccination. rabies vaccine, at any time it is medically indicated, is not exclusionary. prior receipt of another approved or authorized covid-19 vaccine prior to booster injection is not exclusionary in the booster amendment. such participants must provide documentation of vaccine and date(s) of administration. autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) or therapy that causes clinically significant immunosuppression. note: stable endocrine disorders (eg, thyroiditis, pancreatitis, including stable diabetes mellitus) are not excluded. chronic administration (defined as > 14 continuous days) of immunosuppressant or systemic glucocorticoids causing clinically significant immunocompromise, within 90 days prior to first study vaccination and/or third (booster) vaccination. note: an immunosuppressant dose of glucocorticoid is defined as a systemic dose ≥ 20 mg of prednisone per day or equivalent. the use of topical, inhaled, and nasal glucocorticoids is permitted. topical tacrolimus and ocular cyclosporin are permitted. received immunoglobulin or blood-derived products, within 90 days prior to first study vaccination and/or third (booster) vaccination. active cancer (malignancy) on chemotherapy that is judged to cause clinically significant immunocompromise within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). this criterion is not applicable to participants diagnosed during participation in this trial who accept participation in the booster amendment. any known allergies to products contained in the investigational product. participants who are breastfeeding, pregnant or who plan to become pregnant within 3 months following last study vaccination. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). current participation in any other covid-19 prevention clinical trial. adult participants who have not received a full dose of any authorized/approved covid-19 vaccine and are unable to provide valid documentation of vaccination will be excluded from the booster amendment.

adult and pediatric participants meeting any of the following criteria will be excluded from the study: unstable acute or chronic illness. criteria for unstable medical conditions include: substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. note: well-controlled human immunodeficiency virus [hiv] with undetectable hiv rna [< 50 copies/ml] and cd4 count > 200 cells/µl for at least 1 year, documented within the last 6 months, is not considered an unstable chronic illness. participant's or parent's/caregiver's verbal report will suffice as documentation. participation in research involving an investigational product (drug/biologic/device) administered within 45 days prior to first study vaccination. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. a previous diagnosis of covid-19 during participation in this trial is not exclusionary for the booster amendment. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (i.e., 28 days after second vaccination), except for influenza vaccination, which may be received ≥ 4 days prior to or ≥ 7 days after either study vaccination. rabies vaccine, at any time it is medically indicated, is not exclusionary. prior receipt of another approved or authorized covid-19 vaccine prior to booster injection is not exclusionary in the booster amendment. such participants must provide documentation of vaccine and date(s) of administration. autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) or therapy that causes clinically significant immunosuppression. note: stable endocrine disorders (eg, thyroiditis, pancreatitis, including stable diabetes mellitus) are not excluded. chronic administration (defined as > 14 continuous days) of immunosuppressant or systemic glucocorticoids causing clinically significant immunocompromise, within 90 days prior to first study vaccination and/or third (booster) vaccination. note: an immunosuppressant dose of glucocorticoid is defined as a systemic dose ≥ 20 mg of prednisone per day or equivalent. the use of topical, inhaled, and nasal glucocorticoids is permitted. topical tacrolimus and ocular cyclosporin are permitted. received immunoglobulin or blood-derived products, within 90 days prior to first study vaccination and/or third (booster) vaccination. active cancer (malignancy) on chemotherapy that is judged to cause clinically significant immunocompromise within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). this criterion is not applicable to participants diagnosed during participation in this trial who accept participation in the booster amendment. any known allergies to products contained in the investigational product. participants who are breastfeeding, pregnant or who plan to become pregnant within 3 months following last study vaccination. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). current participation in any other covid-19 prevention clinical trial. adult participants who have not received a full dose of any authorized/approved covid-19 vaccine and are unable to provide valid documentation of vaccination will be excluded from the booster amendment.

adult and pediatric participants meeting any of the following criteria will be excluded from the study: unstable acute or chronic illness. criteria for unstable medical conditions include: substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. currently undergoing workup of undiagnosed illness that could lead to a diagnosis of a new condition. participation in research involving an investigational product (drug/biologic/device) within 45 days prior to the first study vaccination. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. received influenza vaccination or any other adult vaccine within 4 days prior to or within 7 days after either study vaccination. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (ie, 28 days after second vaccination). autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) requiring ongoing immunomodulatory therapy. chronic administration (defined as > 14 continuous days) of immunosuppressants, systemic glucocorticoids, or other immune-modifying drugs causing clinically significant immunocompromise, within 90 days prior to first study vaccination. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to first study vaccination. active cancer (malignancy) on therapy within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). this criterion is not applicable to participants diagnosed during participation in this trial who accept participation in the adult main study with booster amendment. any known allergies to products contained in the investigational product. participants who are breastfeeding, pregnant or who plan to become pregnant within 3 months following last study vaccination. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). current participation in any other covid-19 prevention clinical trial.

adult and pediatric participants meeting any of the following criteria will be excluded from the study: unstable acute or chronic illness. criteria for unstable medical conditions include: substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. currently undergoing workup of undiagnosed illness that could lead to a diagnosis of a new condition. participation in research involving an investigational product (drug/biologic/device) within 45 days prior to the first study vaccination. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. received influenza vaccination or any other adult vaccine within 4 days prior to or within 7 days after either study vaccination. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (ie, 28 days after second vaccination). autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) requiring ongoing immunomodulatory therapy. chronic administration (defined as > 14 continuous days) of immunosuppressants, systemic glucocorticoids, or other immune-modifying drugs causing clinically significant immunocompromise, within 90 days prior to first study vaccination. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to first study vaccination. active cancer (malignancy) on therapy within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). this criterion is not applicable to participants diagnosed during participation in this trial who accept participation in the adult main study with booster amendment. any known allergies to products contained in the investigational product. participants who are breastfeeding, pregnant or who plan to become pregnant within 3 months following last study vaccination. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). current participation in any other covid-19 prevention clinical trial.

adult and pediatric participants meeting any of the following criteria will be excluded from the study: unstable acute or chronic illness. criteria for unstable medical conditions include: substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. participation in research involving an investigational product (drug/biologic/device) within 45 days prior to first study vaccination. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. received influenza vaccination or any other adult vaccine within 4 days prior to or within 7 days after either study vaccination. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (ie, 28 days after second vaccination). autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) requiring ongoing immunomodulatory therapy. chronic administration (defined as > 14 continuous days) of immunosuppressant, systemic glucocorticoids, or other immune-modifying drugs within 90 days prior to first study vaccination. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to first study vaccination. active cancer (malignancy) on therapy within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). any known allergies to products contained in the investigational product. participants who are breastfeeding, pregnant or who plan to become pregnant within 3 months following last study vaccination. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). current participation in any other covid-19 prevention clinical trial.

adult and pediatric participants meeting any of the following criteria will be excluded from the study: unstable acute or chronic illness. criteria for unstable medical conditions include: substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. participation in research involving an investigational product (drug/biologic/device) within 45 days prior to first study vaccination. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. received influenza vaccination or any other adult vaccine within 4 days prior to or within 7 days after either study vaccination. received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (ie, 28 days after second vaccination). autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) requiring ongoing immunomodulatory therapy. chronic administration (defined as > 14 continuous days) of immunosuppressant, systemic glucocorticoids, or other immune-modifying drugs within 90 days prior to first study vaccination. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to first study vaccination. active cancer (malignancy) on therapy within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). any known allergies to products contained in the investigational product. participants who are breastfeeding, pregnant or who plan to become pregnant within 3 months following last study vaccination. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). current participation in any other covid-19 prevention clinical trial.

adult and pediatric participants meeting any of the following criteria will be excluded from the study: 1. unstable acute or chronic illness. criteria for unstable medical conditions include: 1. substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. 2. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. 2. participation in research involving an investigational product (drug/biologic/device) within 45 days prior to first study vaccination. 3. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. 4. received influenza vaccination or any other adult vaccine within 4 days prior to or within 7 days after either study vaccination.received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (ie, 28 days after second vaccination). 5. autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) requiring ongoing immunomodulatory therapy. 6. chronic administration (defined as > 14 continuous days) of immunosuppressant, systemic glucocorticoids, or other immune-modifying drugs within 90 days prior to first study vaccination. 7. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to first study vaccination. 8. active cancer (malignancy) on therapy within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). 9. any known allergies to products contained in the investigational product. 10. participants who are breastfeeding, pregnant or who plan to become pregnant within 3 months following last study vaccination. 11. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. 12. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). 13. current participation in any other covid-19 prevention clinical trial.

adult and pediatric participants meeting any of the following criteria will be excluded from the study: 1. unstable acute or chronic illness. criteria for unstable medical conditions include: 1. substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. 2. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. 2. participation in research involving an investigational product (drug/biologic/device) within 45 days prior to first study vaccination. 3. history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. 4. received influenza vaccination or any other adult vaccine within 4 days prior to or within 7 days after either study vaccination.received any vaccine within 4 days prior to first study vaccination or planned receipt of any vaccine before day 49 (ie, 28 days after second vaccination). 5. autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) requiring ongoing immunomodulatory therapy. 6. chronic administration (defined as > 14 continuous days) of immunosuppressant, systemic glucocorticoids, or other immune-modifying drugs within 90 days prior to first study vaccination. 7. received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to first study vaccination. 8. active cancer (malignancy) on therapy within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). 9. any known allergies to products contained in the investigational product. 10. participants who are breastfeeding, pregnant or who plan to become pregnant within 3 months following last study vaccination. 11. any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. 12. study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). 13. current participation in any other covid-19 prevention clinical trial.

- unstable acute or chronic illness. criteria for unstable medical conditions include: 1. substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. 2. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. - participation in research involving an investigational product (drug/biologic/device) within 45 days prior to first study vaccination. - history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. - received influenza vaccination or any other adult vaccine within 4 days prior to or within 7 days after either study vaccination. - autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) requiring ongoing immunomodulatory therapy. - chronic administration (defined as > 14 continuous days) of immunosuppressant, systemic glucocorticoids, or other immune-modifying drugs within 90 days prior to first study vaccination. - received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to first study vaccination. - active cancer (malignancy) on therapy within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). - any known allergies to products contained in the investigational product. - participants who are breastfeeding, pregnant or who plan to become pregnant within 3 months following last study vaccination. - any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. - study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). - current participation in any other covid-19 prevention clinical trial.

- unstable acute or chronic illness. criteria for unstable medical conditions include: 1. substantive changes in chronic prescribed medication (change in class or significant change in dose) in the past 2 months. 2. currently undergoing workup of undiagnosed illness that could lead to diagnosis of a new condition. - participation in research involving an investigational product (drug/biologic/device) within 45 days prior to first study vaccination. - history of a previous laboratory-confirmed diagnosis of sars-cov-2 infection or covid-19. - received influenza vaccination or any other adult vaccine within 4 days prior to or within 7 days after either study vaccination. - autoimmune or immunodeficiency disease/condition (iatrogenic or congenital) requiring ongoing immunomodulatory therapy. - chronic administration (defined as > 14 continuous days) of immunosuppressant, systemic glucocorticoids, or other immune-modifying drugs within 90 days prior to first study vaccination. - received immunoglobulin, blood-derived products, or immunosuppressant drugs within 90 days prior to first study vaccination. - active cancer (malignancy) on therapy within 1 year prior to first study vaccination (with the exception of malignancy cured via excision, at the discretion of the investigator). - any known allergies to products contained in the investigational product. - participants who are breastfeeding, pregnant or who plan to become pregnant within 3 months following last study vaccination. - any other condition that, in the opinion of the investigator, would pose a health risk to the participant if enrolled or could interfere with evaluation of the trial vaccine or interpretation of study results. - study team member or first-degree relative of any study team member (inclusive of sponsor, and study site personnel involved in the study). - current participation in any other covid-19 prevention clinical trial.