* history of virologically-confirmed covid-19 illness. * for females: pregnancy or lactation. * use of any investigational or non-registered product (vaccine or drug) within 28 days preceding the administration of trial vaccine or planned use during the trial. * receipt of any licensed vaccines within 28 days (for live vaccines) or 14 days (for inactivated or any other vaccines) prior to administration of the first trial vaccine. * prior administration of any investigational sars-cov-2 vaccine or another coronavirus (sars-cov, middle east respiratory syndrome-cov) vaccine or planned used during the trial. * any treatment with immunosuppressants or other immune-modifying drugs (including but not limited to anabolic steroids, corticosteroids, biologicals and methotrexate) for \> 14 days total within 6 months preceding the administration of trial vaccine or planned use during the trial. for corticosteroid use, this means prednisone or equivalent, 0.5 mg/kg/day for 14 days or more. the use of inhaled, topical, or localized injections of corticosteroids (e.g., for joint pain/inflammation) is permitted. * any medically diagnosed or suspected immunosuppressive or immunodeficient condition based on medical history and physical examination including known infection with human immunodeficiency virus (hiv), hepatitis b virus (hbv) or hepatitis c virus (hcv); current diagnosis of or treatment for cancer including leukemia, lymphoma, hodgkin disease, multiple myeloma or generalized malignancy; chronic renal failure or nephrotic syndrome; and receipt of an organ or bone marrow transplant. * history of angioedema (hereditary or idiopathic) or history of any anaphylactic reaction. * history of potential immune-mediated disease (pimd). * history of allergy to any component of cvncov. * administration of immunoglobulins or any blood products within 3 months prior to the administration of trial vaccine or planned receipt during the trial. * participants with a significant acute or chronic medical or psychiatric illness that, in the opinion of the investigator, precludes trial participation (e.g., may increase the risk of trial participation, render the participant unable to meet the requirements of the trial, or may interfere with the participant's trial evaluations). these include severe and/or uncontrolled cardiovascular disease, gastrointestinal disease, liver disease, renal disease, respiratory disease, endocrine disorder, and neurological and psychiatric illnesses. however, those with controlled and stable cases can be included in the trial. * participants with impaired coagulation or any bleeding disorder in whom an im injection or a blood draw is contraindicated. * foreseeable non-compliance with the trial procedure as judged by the investigator. roll-over criteria for the open-label phase: * participants must have received at least 1 dose of cvncov during the randomized observer blinded phase. * participants must provide additional written informed consent to be eligible for the open label phase.

* history of virologically-confirmed covid-19 illness. * for females: pregnancy or lactation. * use of any investigational or non-registered product (vaccine or drug) within 28 days preceding the administration of trial vaccine or planned use during the trial. * receipt of any licensed vaccines within 28 days (for live vaccines) or 14 days (for inactivated or any other vaccines) prior to administration of the first trial vaccine. * prior administration of any investigational sars-cov-2 vaccine or another coronavirus (sars-cov, middle east respiratory syndrome-cov) vaccine or planned used during the trial. * any treatment with immunosuppressants or other immune-modifying drugs (including but not limited to anabolic steroids, corticosteroids, biologicals and methotrexate) for \> 14 days total within 6 months preceding the administration of trial vaccine or planned use during the trial. for corticosteroid use, this means prednisone or equivalent, 0.5 mg/kg/day for 14 days or more. the use of inhaled, topical, or localized injections of corticosteroids (e.g., for joint pain/inflammation) is permitted. * any medically diagnosed or suspected immunosuppressive or immunodeficient condition based on medical history and physical examination including known infection with human immunodeficiency virus (hiv), hepatitis b virus (hbv) or hepatitis c virus (hcv); current diagnosis of or treatment for cancer including leukemia, lymphoma, hodgkin disease, multiple myeloma or generalized malignancy; chronic renal failure or nephrotic syndrome; and receipt of an organ or bone marrow transplant. * history of angioedema (hereditary or idiopathic) or history of any anaphylactic reaction. * history of potential immune-mediated disease (pimd). * history of allergy to any component of cvncov. * administration of immunoglobulins or any blood products within 3 months prior to the administration of trial vaccine or planned receipt during the trial. * participants with a significant acute or chronic medical or psychiatric illness that, in the opinion of the investigator, precludes trial participation (e.g., may increase the risk of trial participation, render the participant unable to meet the requirements of the trial, or may interfere with the participant's trial evaluations). these include severe and/or uncontrolled cardiovascular disease, gastrointestinal disease, liver disease, renal disease, respiratory disease, endocrine disorder, and neurological and psychiatric illnesses. however, those with controlled and stable cases can be included in the trial. * participants with impaired coagulation or any bleeding disorder in whom an im injection or a blood draw is contraindicated. * foreseeable non-compliance with the trial procedure as judged by the investigator. roll-over criteria for the open-label phase: * participants must have received at least 1 dose of cvncov during the randomized observer blinded phase. * participants must provide additional written informed consent to be eligible for the open label phase.

history of virologically-confirmed covid-19 illness. for females: pregnancy or lactation. use of any investigational or non-registered product (vaccine or drug) within 28 days preceding the administration of trial vaccine or planned use during the trial. receipt of any licensed vaccines within 28 days (for live vaccines) or 14 days (for inactivated or any other vaccines) prior to administration of the first trial vaccine. prior administration of any investigational sars-cov-2 vaccine or another coronavirus (sars-cov, middle east respiratory syndrome-cov) vaccine or planned used during the trial. any treatment with immunosuppressants or other immune-modifying drugs (including but not limited to anabolic steroids, corticosteroids, biologicals and methotrexate) for > 14 days total within 6 months preceding the administration of trial vaccine or planned use during the trial. for corticosteroid use, this means prednisone or equivalent, 0.5 mg/kg/day for 14 days or more. the use of inhaled, topical, or localized injections of corticosteroids (e.g., for joint pain/inflammation) is permitted. any medically diagnosed or suspected immunosuppressive or immunodeficient condition based on medical history and physical examination including known infection with human immunodeficiency virus (hiv), hepatitis b virus (hbv) or hepatitis c virus (hcv); current diagnosis of or treatment for cancer including leukemia, lymphoma, hodgkin disease, multiple myeloma or generalized malignancy; chronic renal failure or nephrotic syndrome; and receipt of an organ or bone marrow transplant. history of angioedema (hereditary or idiopathic) or history of any anaphylactic reaction. history of potential immune-mediated disease (pimd). history of allergy to any component of cvncov. administration of immunoglobulins or any blood products within 3 months prior to the administration of trial vaccine or planned receipt during the trial. participants with a significant acute or chronic medical or psychiatric illness that, in the opinion of the investigator, precludes trial participation (e.g., may increase the risk of trial participation, render the participant unable to meet the requirements of the trial, or may interfere with the participant's trial evaluations). these include severe and/or uncontrolled cardiovascular disease, gastrointestinal disease, liver disease, renal disease, respiratory disease, endocrine disorder, and neurological and psychiatric illnesses. however, those with controlled and stable cases can be included in the trial. participants with impaired coagulation or any bleeding disorder in whom an im injection or a blood draw is contraindicated. foreseeable non-compliance with the trial procedure as judged by the investigator. roll-over criteria for the open-label phase: participants must have received at least 1 dose of cvncov during the randomized observer blinded phase. participants must provide additional written informed consent to be eligible for the open label phase.

history of virologically-confirmed covid-19 illness. for females: pregnancy or lactation. use of any investigational or non-registered product (vaccine or drug) within 28 days preceding the administration of trial vaccine or planned use during the trial. receipt of any licensed vaccines within 28 days (for live vaccines) or 14 days (for inactivated or any other vaccines) prior to administration of the first trial vaccine. prior administration of any investigational sars-cov-2 vaccine or another coronavirus (sars-cov, middle east respiratory syndrome-cov) vaccine or planned used during the trial. any treatment with immunosuppressants or other immune-modifying drugs (including but not limited to anabolic steroids, corticosteroids, biologicals and methotrexate) for > 14 days total within 6 months preceding the administration of trial vaccine or planned use during the trial. for corticosteroid use, this means prednisone or equivalent, 0.5 mg/kg/day for 14 days or more. the use of inhaled, topical, or localized injections of corticosteroids (e.g., for joint pain/inflammation) is permitted. any medically diagnosed or suspected immunosuppressive or immunodeficient condition based on medical history and physical examination including known infection with human immunodeficiency virus (hiv), hepatitis b virus (hbv) or hepatitis c virus (hcv); current diagnosis of or treatment for cancer including leukemia, lymphoma, hodgkin disease, multiple myeloma or generalized malignancy; chronic renal failure or nephrotic syndrome; and receipt of an organ or bone marrow transplant. history of angioedema (hereditary or idiopathic) or history of any anaphylactic reaction. history of potential immune-mediated disease (pimd). history of allergy to any component of cvncov. administration of immunoglobulins or any blood products within 3 months prior to the administration of trial vaccine or planned receipt during the trial. participants with a significant acute or chronic medical or psychiatric illness that, in the opinion of the investigator, precludes trial participation (e.g., may increase the risk of trial participation, render the participant unable to meet the requirements of the trial, or may interfere with the participant's trial evaluations). these include severe and/or uncontrolled cardiovascular disease, gastrointestinal disease, liver disease, renal disease, respiratory disease, endocrine disorder, and neurological and psychiatric illnesses. however, those with controlled and stable cases can be included in the trial. participants with impaired coagulation or any bleeding disorder in whom an im injection or a blood draw is contraindicated. foreseeable non-compliance with the trial procedure as judged by the investigator. roll-over criteria for the open-label phase: participants must have received at least 1 dose of cvncov during the randomized observer blinded phase. participants must provide additional written informed consent to be eligible for the open label phase.

- history of virologically-confirmed covid-19 illness. - for females: pregnancy or lactation. - use of any investigational or non-registered product (vaccine or drug) within 28 days preceding the administration of trial vaccine or planned use during the trial. - receipt of any licensed vaccines within 28 days (for live vaccines) or 14 days (for inactivated or any other vaccines) prior to administration of the first trial vaccine. - prior administration of any investigational sars-cov-2 vaccine or another coronavirus (sars-cov, middle east respiratory syndrome-cov) vaccine or planned used during the trial. - any treatment with immunosuppressants or other immune-modifying drugs (including but not limited to anabolic steroids, corticosteroids, biologicals and methotrexate) for > 14 days total within 6 months preceding the administration of trial vaccine or planned use during the trial. for corticosteroid use, this means prednisone or equivalent, 0.5 mg/kg/day for 14 days or more. the use of inhaled, topical, or localized injections of corticosteroids (e.g., for joint pain/inflammation) is permitted. - any medically diagnosed or suspected immunosuppressive or immunodeficient condition based on medical history and physical examination including known infection with human immunodeficiency virus (hiv), hepatitis b virus (hbv) or hepatitis c virus (hcv); current diagnosis of or treatment for cancer including leukemia, lymphoma, hodgkin disease, multiple myeloma or generalized malignancy; chronic renal failure or nephrotic syndrome; and receipt of an organ or bone marrow transplant. - history of angioedema (hereditary or idiopathic) or history of any anaphylactic reaction. - history of potential immune-mediated disease (pimd). - history of allergy to any component of cvncov. - administration of immunoglobulins or any blood products within 3 months prior to the administration of trial vaccine or planned receipt during the trial. - participants with a significant acute or chronic medical or psychiatric illness that, in the opinion of the investigator, precludes trial participation (e.g., may increase the risk of trial participation, render the participant unable to meet the requirements of the trial, or may interfere with the participant's trial evaluations). these include severe and/or uncontrolled cardiovascular disease, gastrointestinal disease, liver disease, renal disease, respiratory disease, endocrine disorder, and neurological and psychiatric illnesses. however, those with controlled and stable cases can be included in the trial. - participants with impaired coagulation or any bleeding disorder in whom an intramuscular injection or a blood draw is contraindicated. - foreseeable non-compliance with the trial procedure as judged by the investigator.

- history of virologically-confirmed covid-19 illness. - for females: pregnancy or lactation. - use of any investigational or non-registered product (vaccine or drug) within 28 days preceding the administration of trial vaccine or planned use during the trial. - receipt of any licensed vaccines within 28 days (for live vaccines) or 14 days (for inactivated or any other vaccines) prior to administration of the first trial vaccine. - prior administration of any investigational sars-cov-2 vaccine or another coronavirus (sars-cov, middle east respiratory syndrome-cov) vaccine or planned used during the trial. - any treatment with immunosuppressants or other immune-modifying drugs (including but not limited to anabolic steroids, corticosteroids, biologicals and methotrexate) for > 14 days total within 6 months preceding the administration of trial vaccine or planned use during the trial. for corticosteroid use, this means prednisone or equivalent, 0.5 mg/kg/day for 14 days or more. the use of inhaled, topical, or localized injections of corticosteroids (e.g., for joint pain/inflammation) is permitted. - any medically diagnosed or suspected immunosuppressive or immunodeficient condition based on medical history and physical examination including known infection with human immunodeficiency virus (hiv), hepatitis b virus (hbv) or hepatitis c virus (hcv); current diagnosis of or treatment for cancer including leukemia, lymphoma, hodgkin disease, multiple myeloma or generalized malignancy; chronic renal failure or nephrotic syndrome; and receipt of an organ or bone marrow transplant. - history of angioedema (hereditary or idiopathic) or history of any anaphylactic reaction. - history of potential immune-mediated disease (pimd). - history of allergy to any component of cvncov. - administration of immunoglobulins or any blood products within 3 months prior to the administration of trial vaccine or planned receipt during the trial. - participants with a significant acute or chronic medical or psychiatric illness that, in the opinion of the investigator, precludes trial participation (e.g., may increase the risk of trial participation, render the participant unable to meet the requirements of the trial, or may interfere with the participant's trial evaluations). these include severe and/or uncontrolled cardiovascular disease, gastrointestinal disease, liver disease, renal disease, respiratory disease, endocrine disorder, and neurological and psychiatric illnesses. however, those with controlled and stable cases can be included in the trial. - participants with impaired coagulation or any bleeding disorder in whom an intramuscular injection or a blood draw is contraindicated. - foreseeable non-compliance with the trial procedure as judged by the investigator.

- history of virologically-confirmed covid-19 illness. - for females: pregnancy or lactation. - use of any investigational or non-registered product (vaccine or drug) within 28 days preceding the administration of trial vaccine or planned use during the trial. - receipt of any licensed vaccines within 28 days (for live vaccines) or 14 days (for inactivated vaccines) prior to administration of the first trial vaccine. - prior administration of any investigational sars-cov-2 vaccine or another coronavirus (sars-cov, mers-cov) vaccine or planned used during the trial. - any treatment with immunosuppressants or other immune-modifying drugs (including but not limited to corticosteroids, biologicals and methotrexate) for > 14 days total within 6 months preceding the administration of trial vaccine or planned use during the trial. for corticosteroid use, this means prednisone or equivalent, 0.5 mg/kg/day for 14 days or more. the use of inhaled, topical, or localized injections of corticosteroids (e.g., for joint pain/inflammation) is permitted. - any medically diagnosed or suspected immunosuppressive or immunodeficient condition based on medical history and physical examination including known infection with human immunodeficiency virus (hiv), hepatitis b virus (hbv) or hepatitis c virus (hcv); current diagnosis of or treatment for cancer including leukemia, lymphoma, hodgkin disease, multiple myeloma or generalized malignancy; chronic renal failure or nephrotic syndrome; and receipt of an organ or bone marrow transplant. - history of angioedema (hereditary or idiopathic), any anaphylactic reactions or pimd. - history of allergy to any component of cvncov. - administration of immunoglobulins or any blood products within 3 months prior to the administration of trial vaccine or planned receipt during the trial. - participants with a significant acute or chronic medical or psychiatric illness that, in the opinion of the investigator, precludes trial participation (e.g., may increase the risk of trial participation, render the participant unable to meet the requirements of the trial, or may interfere with the participant's trial evaluations). these include severe and/or uncontrolled cardiovascular disease, gastrointestinal disease, liver disease, renal disease, respiratory disease, endocrine disorder, and neurological and psychiatric illnesses. however, those with controlled and stable cases can be included in the trial. - participants with impaired coagulation or any bleeding disorder in whom an intramuscular injection or a blood draw is contraindicated. - foreseeable non-compliance with the trial procedure as judged by the investigator.

- history of virologically-confirmed covid-19 illness. - for females: pregnancy or lactation. - use of any investigational or non-registered product (vaccine or drug) within 28 days preceding the administration of trial vaccine or planned use during the trial. - receipt of any licensed vaccines within 28 days (for live vaccines) or 14 days (for inactivated vaccines) prior to administration of the first trial vaccine. - prior administration of any investigational sars-cov-2 vaccine or another coronavirus (sars-cov, mers-cov) vaccine or planned used during the trial. - any treatment with immunosuppressants or other immune-modifying drugs (including but not limited to corticosteroids, biologicals and methotrexate) for > 14 days total within 6 months preceding the administration of trial vaccine or planned use during the trial. for corticosteroid use, this means prednisone or equivalent, 0.5 mg/kg/day for 14 days or more. the use of inhaled, topical, or localized injections of corticosteroids (e.g., for joint pain/inflammation) is permitted. - any medically diagnosed or suspected immunosuppressive or immunodeficient condition based on medical history and physical examination including known infection with human immunodeficiency virus (hiv), hepatitis b virus (hbv) or hepatitis c virus (hcv); current diagnosis of or treatment for cancer including leukemia, lymphoma, hodgkin disease, multiple myeloma or generalized malignancy; chronic renal failure or nephrotic syndrome; and receipt of an organ or bone marrow transplant. - history of angioedema (hereditary or idiopathic), any anaphylactic reactions or pimd. - history of allergy to any component of cvncov. - administration of immunoglobulins or any blood products within 3 months prior to the administration of trial vaccine or planned receipt during the trial. - participants with a significant acute or chronic medical or psychiatric illness that, in the opinion of the investigator, precludes trial participation (e.g., may increase the risk of trial participation, render the participant unable to meet the requirements of the trial, or may interfere with the participant's trial evaluations). these include severe and/or uncontrolled cardiovascular disease, gastrointestinal disease, liver disease, renal disease, respiratory disease, endocrine disorder, and neurological and psychiatric illnesses. however, those with controlled and stable cases can be included in the trial. - participants with impaired coagulation or any bleeding disorder in whom an intramuscular injection or a blood draw is contraindicated. - foreseeable non-compliance with the trial procedure as judged by the investigator.