* history of prior confirmed covid-19 (cohorts 1 and 2). * history of prior confirmed (polymerase chain reaction \[pcr\] or antigen test positive) covid-19 infection as confirmed by a diagnostic laboratory less than 16 weeks (112 days) prior to enrollment (cohorts 3, 4, and 6). * positive for sars-cov-2 (n-specific) antibody testing and had a history of upper respiratory illness consistent with covid-19 within the 112 days prior to enrollment (cohorts 3, 4, and 6). * prior receipt of a sars-cov-2 vaccine other than astrazeneca's azd1222 (covishield®, vaxzevria®), jnj-78436735, pfizer/biontech (comirnaty®), moderna (spikevax®), other approved or investigational adenovirus vectored vaccines, approved or investigational vaccines with a lipid nanoparticle (lnp) component, or any other approved or investigational vaccine likely to impact the interpretation of the trial data. * on current treatment or prevention agents with activity against sars-cov-2. * participation in another research study involving receipt of an investigational product in the 60 days preceding enrollment or planned use during the study period. * receipt or planned receipt of any live, attenuated vaccine within 28 days before or after study vaccination. * receipt or planned receipt of any subunit or killed vaccine within 14 days before or after vaccination. * administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of first study vaccination or at any time during the study. * breastfeeding, pregnant, or planning to become pregnant during the course of the study. * any confirmed or suspected immunosuppressive or immunodeficient state, including hiv infection with cd4+ t-cells \< 400/mm3, asplenia, recurrent, severe infections and chronic (more than 14 continuous days) immunosuppressant medication within the past 6 months (inhaled, ophthalmic, and topical steroids are allowed). * history of allergic disease or reactions likely to be exacerbated by any component of the vaccine, including urticaria, respiratory difficulty or abdominal pain (or any immediate allergic reaction of any severity to polysorbate due to potential cross-reactive hypersensitivity with the peg component of the vaccine). * any history of hereditary angioedema, acquired angioedema, or idiopathic angioedema. * any history of anaphylaxis, including but not limited to reaction to vaccination. * history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). * history of serious ongoing, unstable psychiatric condition that in the opinion of the investigator would interfere with study participation. * bleeding disorder or prior history of significant bleeding or bruising following im injections or venipuncture. * suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. * suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. suspected or known drug abuse in the 5 years preceding enrollment. * 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.

* history of prior confirmed covid-19 (cohorts 1 and 2). * history of prior confirmed (polymerase chain reaction \[pcr\] or antigen test positive) covid-19 infection as confirmed by a diagnostic laboratory less than 16 weeks (112 days) prior to enrollment (cohorts 3, 4, and 6). * positive for sars-cov-2 (n-specific) antibody testing and had a history of upper respiratory illness consistent with covid-19 within the 112 days prior to enrollment (cohorts 3, 4, and 6). * prior receipt of a sars-cov-2 vaccine other than astrazeneca's azd1222 (covishield®, vaxzevria®), jnj-78436735, pfizer/biontech (comirnaty®), moderna (spikevax®), other approved or investigational adenovirus vectored vaccines, approved or investigational vaccines with a lipid nanoparticle (lnp) component, or any other approved or investigational vaccine likely to impact the interpretation of the trial data. * on current treatment or prevention agents with activity against sars-cov-2. * participation in another research study involving receipt of an investigational product in the 60 days preceding enrollment or planned use during the study period. * receipt or planned receipt of any live, attenuated vaccine within 28 days before or after study vaccination. * receipt or planned receipt of any subunit or killed vaccine within 14 days before or after vaccination. * administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of first study vaccination or at any time during the study. * breastfeeding, pregnant, or planning to become pregnant during the course of the study. * any confirmed or suspected immunosuppressive or immunodeficient state, including hiv infection with cd4+ t-cells \< 400/mm3, asplenia, recurrent, severe infections and chronic (more than 14 continuous days) immunosuppressant medication within the past 6 months (inhaled, ophthalmic, and topical steroids are allowed). * history of allergic disease or reactions likely to be exacerbated by any component of the vaccine, including urticaria, respiratory difficulty or abdominal pain (or any immediate allergic reaction of any severity to polysorbate due to potential cross-reactive hypersensitivity with the peg component of the vaccine). * any history of hereditary angioedema, acquired angioedema, or idiopathic angioedema. * any history of anaphylaxis, including but not limited to reaction to vaccination. * history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). * history of serious ongoing, unstable psychiatric condition that in the opinion of the investigator would interfere with study participation. * bleeding disorder or prior history of significant bleeding or bruising following im injections or venipuncture. * suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. * suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. suspected or known drug abuse in the 5 years preceding enrollment. * 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.

* history of prior confirmed covid-19 (cohorts 1 and 2). * positive for sars-cov-2 by lateral flow test (rapid diagnostic test), enzyme-linked immunosorbent assay (elisa) or by nasal swab polymerase chain reaction (pcr) at screening (cohorts 3-6). * prior receipt of a sars-cov-2 vaccine other than astrazeneca's azd1222 (covishield®, vaxzevria®), jnj-78436735, pfizer/biontech (comirnaty®), moderna (spikevax®), other approved or investigational adenovirus vectored vaccines, approved or investigational vaccines with a lipid nanoparticle (lnp) component, or any other approved or investigational vaccine likely to impact the interpretation of the trial data. * on current treatment or prevention agents with activity against sars-cov-2. * participation in another research study involving receipt of an investigational product in the 60 days preceding enrollment or planned use during the study period. * receipt or planned receipt of any live, attenuated vaccine within 28 days before or after study vaccination. * receipt or planned receipt of any subunit or killed vaccine within 14 days before or after vaccination. * administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of first study vaccination or at any time during the study. * any confirmed or suspected immunosuppressive or immunodeficient state. * history of allergic disease or reactions likely to be exacerbated by any component of the vaccine, including urticaria, respiratory difficulty or abdominal pain. * any history of hereditary angioedema, acquired angioedema, or idiopathic angioedema. * any history of anaphylaxis, including but not limited to reaction to vaccination. * history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). * history of serious ongoing, unstable psychiatric condition that in the opinion of the investigator would interfere with study participation. * bleeding disorder or prior history of significant bleeding or bruising following im injections or venipuncture. * suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. * suspected or known drug abuse in the 5 years preceding enrollment. * 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.

* history of prior confirmed covid-19 (cohorts 1 and 2). * positive for sars-cov-2 by lateral flow test (rapid diagnostic test), enzyme-linked immunosorbent assay (elisa) or by nasal swab polymerase chain reaction (pcr) at screening (cohorts 3-6). * prior receipt of a sars-cov-2 vaccine other than astrazeneca's azd1222 (covishield®, vaxzevria®), jnj-78436735, pfizer/biontech (comirnaty®), moderna (spikevax®), other approved or investigational adenovirus vectored vaccines, approved or investigational vaccines with a lipid nanoparticle (lnp) component, or any other approved or investigational vaccine likely to impact the interpretation of the trial data. * on current treatment or prevention agents with activity against sars-cov-2. * participation in another research study involving receipt of an investigational product in the 60 days preceding enrollment or planned use during the study period. * receipt or planned receipt of any live, attenuated vaccine within 28 days before or after study vaccination. * receipt or planned receipt of any subunit or killed vaccine within 14 days before or after vaccination. * administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of first study vaccination or at any time during the study. * any confirmed or suspected immunosuppressive or immunodeficient state. * history of allergic disease or reactions likely to be exacerbated by any component of the vaccine, including urticaria, respiratory difficulty or abdominal pain. * any history of hereditary angioedema, acquired angioedema, or idiopathic angioedema. * any history of anaphylaxis, including but not limited to reaction to vaccination. * history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). * history of serious ongoing, unstable psychiatric condition that in the opinion of the investigator would interfere with study participation. * bleeding disorder or prior history of significant bleeding or bruising following im injections or venipuncture. * suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. * suspected or known drug abuse in the 5 years preceding enrollment. * 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.

history of prior confirmed covid-19 (cohorts 1 and 2). positive for sars-cov-2 by lateral flow test (rapid diagnostic test), enzyme-linked immunosorbent assay (elisa) or by nasal swab polymerase chain reaction (pcr) at screening (cohorts 3-6). prior receipt of a sars-cov-2 vaccine other than astrazeneca's azd1222 (covishield®, vaxzevria®), jnj-78436735, pfizer/biontech (comirnaty®), moderna (spikevax®), other approved or investigational adenovirus vectored vaccines, approved or investigational vaccines with a lipid nanoparticle (lnp) component, or any other approved or investigational vaccine likely to impact the interpretation of the trial data. on current treatment or prevention agents with activity against sars-cov-2. participation in another research study involving receipt of an investigational product in the 60 days preceding enrollment or planned use during the study period. receipt or planned receipt of any live, attenuated vaccine within 28 days before or after study vaccination. receipt or planned receipt of any subunit or killed vaccine within 14 days before or after vaccination. administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of first study vaccination or at any time during the study. any confirmed or suspected immunosuppressive or immunodeficient state. history of allergic disease or reactions likely to be exacerbated by any component of the vaccine, including urticaria, respiratory difficulty or abdominal pain. any history of hereditary angioedema, acquired angioedema, or idiopathic angioedema. any history of anaphylaxis, including but not limited to reaction to vaccination. history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). history of serious ongoing, unstable psychiatric condition that in the opinion of the investigator would interfere with study participation. bleeding disorder or prior history of significant bleeding or bruising following im injections or venipuncture. suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. suspected or known drug abuse in the 5 years preceding enrollment. 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.

history of prior confirmed covid-19 (cohorts 1 and 2). positive for sars-cov-2 by lateral flow test (rapid diagnostic test), enzyme-linked immunosorbent assay (elisa) or by nasal swab polymerase chain reaction (pcr) at screening (cohorts 3-6). prior receipt of a sars-cov-2 vaccine other than astrazeneca's azd1222 (covishield®, vaxzevria®), jnj-78436735, pfizer/biontech (comirnaty®), moderna (spikevax®), other approved or investigational adenovirus vectored vaccines, approved or investigational vaccines with a lipid nanoparticle (lnp) component, or any other approved or investigational vaccine likely to impact the interpretation of the trial data. on current treatment or prevention agents with activity against sars-cov-2. participation in another research study involving receipt of an investigational product in the 60 days preceding enrollment or planned use during the study period. receipt or planned receipt of any live, attenuated vaccine within 28 days before or after study vaccination. receipt or planned receipt of any subunit or killed vaccine within 14 days before or after vaccination. administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of first study vaccination or at any time during the study. any confirmed or suspected immunosuppressive or immunodeficient state. history of allergic disease or reactions likely to be exacerbated by any component of the vaccine, including urticaria, respiratory difficulty or abdominal pain. any history of hereditary angioedema, acquired angioedema, or idiopathic angioedema. any history of anaphylaxis, including but not limited to reaction to vaccination. history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). history of serious ongoing, unstable psychiatric condition that in the opinion of the investigator would interfere with study participation. bleeding disorder or prior history of significant bleeding or bruising following im injections or venipuncture. suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. suspected or known drug abuse in the 5 years preceding enrollment. 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.

history of prior confirmed covid-19 (cohorts 1 and 2). positive for sars-cov-2 by lateral flow test (rapid diagnostic test), enzyme-linked immunosorbent assay (elisa) or by nasal swab polymerase chain reaction (pcr) at screening (cohorts 3-6). prior receipt of a sars-cov-2 vaccine other than astrazeneca's azd1222 (covishield®, vaxzevria®), approved or investigational adenovirus vectored vaccines, approved or investigational vaccines with a lipid nanoparticle (lnp) component, or any other approved or investigational vaccine likely to impact the interpretation of the trial data. on current treatment or prevention agents with activity against sars-cov-2. participation in another research study involving receipt of an investigational product in the 60 days preceding enrollment or planned use during the study period. receipt or planned receipt of any live, attenuated vaccine within 28 days before or after study vaccination. receipt or planned receipt of any subunit or killed vaccine within 14 days before or after vaccination. administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of first study vaccination or at any time during the study. any confirmed or suspected immunosuppressive or immunodeficient state. history of allergic disease or reactions likely to be exacerbated by any component of the vaccine, including urticaria, respiratory difficulty or abdominal pain. any history of hereditary angioedema, acquired angioedema, or idiopathic angioedema. any history of anaphylaxis, including but not limited to reaction to vaccination. history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). history of serious ongoing, unstable psychiatric condition that in the opinion of the investigator would interfere with study participation. bleeding disorder or prior history of significant bleeding or bruising following im injections or venipuncture. suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. suspected or known drug abuse in the 5 years preceding enrollment. 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.

history of prior confirmed covid-19 (cohorts 1 and 2). positive for sars-cov-2 by lateral flow test (rapid diagnostic test), enzyme-linked immunosorbent assay (elisa) or by nasal swab polymerase chain reaction (pcr) at screening (cohorts 3-6). prior receipt of a sars-cov-2 vaccine other than astrazeneca's azd1222 (covishield®, vaxzevria®), approved or investigational adenovirus vectored vaccines, approved or investigational vaccines with a lipid nanoparticle (lnp) component, or any other approved or investigational vaccine likely to impact the interpretation of the trial data. on current treatment or prevention agents with activity against sars-cov-2. participation in another research study involving receipt of an investigational product in the 60 days preceding enrollment or planned use during the study period. receipt or planned receipt of any live, attenuated vaccine within 28 days before or after study vaccination. receipt or planned receipt of any subunit or killed vaccine within 14 days before or after vaccination. administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of first study vaccination or at any time during the study. any confirmed or suspected immunosuppressive or immunodeficient state. history of allergic disease or reactions likely to be exacerbated by any component of the vaccine, including urticaria, respiratory difficulty or abdominal pain. any history of hereditary angioedema, acquired angioedema, or idiopathic angioedema. any history of anaphylaxis, including but not limited to reaction to vaccination. history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). history of serious ongoing, unstable psychiatric condition that in the opinion of the investigator would interfere with study participation. bleeding disorder or prior history of significant bleeding or bruising following im injections or venipuncture. suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. suspected or known drug abuse in the 5 years preceding enrollment. 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.

history of prior confirmed covid-19. positive for sars-cov-2 by lateral flow test (rapid diagnostic test), enzyme-linked immunosorbent assay (elisa) or by nasal swab polymerase chain reaction (pcr) at screening. prior receipt of a sars-cov-2 vaccine other than astrazeneca's azd1222 (covishield®, vaxzevria®), approved or investigational adenovirus vectored vaccines, approved or investigational vaccines with a lipid nanoparticle (lnp) component, or any other approved or investigational vaccine likely to impact the interpretation of the trial data. on current treatment or prevention agents with activity against sars-cov-2. participation in another research study involving receipt of an investigational product in the 60 days preceding enrollment or planned use during the study period. receipt or planned receipt of any live, attenuated vaccine within 28 days before or after study vaccination. receipt or planned receipt of any subunit or killed vaccine within 14 days before or after vaccination. administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of first study vaccination or at any time during the study. any confirmed or suspected immunosuppressive or immunodeficient state. history of allergic disease or reactions likely to be exacerbated by any component of the vaccine, including urticaria, respiratory difficulty or abdominal pain. any history of hereditary angioedema, acquired angioedema, or idiopathic angioedema. any history of anaphylaxis, including but not limited to reaction to vaccination. history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). history of serious ongoing, unstable psychiatric condition that in the opinion of the investigator would interfere with study participation. seizure in the past 3 years or treatment for seizure disorder in the past 3 years. bleeding disorder or prior history of significant bleeding or bruising following im injections or venipuncture. suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. suspected or known drug abuse in the 5 years preceding enrollment. 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.

history of prior confirmed covid-19. positive for sars-cov-2 by lateral flow test (rapid diagnostic test), enzyme-linked immunosorbent assay (elisa) or by nasal swab polymerase chain reaction (pcr) at screening. prior receipt of a sars-cov-2 vaccine other than astrazeneca's azd1222 (covishield®, vaxzevria®), approved or investigational adenovirus vectored vaccines, approved or investigational vaccines with a lipid nanoparticle (lnp) component, or any other approved or investigational vaccine likely to impact the interpretation of the trial data. on current treatment or prevention agents with activity against sars-cov-2. participation in another research study involving receipt of an investigational product in the 60 days preceding enrollment or planned use during the study period. receipt or planned receipt of any live, attenuated vaccine within 28 days before or after study vaccination. receipt or planned receipt of any subunit or killed vaccine within 14 days before or after vaccination. administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of first study vaccination or at any time during the study. any confirmed or suspected immunosuppressive or immunodeficient state. history of allergic disease or reactions likely to be exacerbated by any component of the vaccine, including urticaria, respiratory difficulty or abdominal pain. any history of hereditary angioedema, acquired angioedema, or idiopathic angioedema. any history of anaphylaxis, including but not limited to reaction to vaccination. history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). history of serious ongoing, unstable psychiatric condition that in the opinion of the investigator would interfere with study participation. seizure in the past 3 years or treatment for seizure disorder in the past 3 years. bleeding disorder or prior history of significant bleeding or bruising following im injections or venipuncture. suspected or known current alcohol abuse that in the opinion of the investigator would impede compliance with the protocol and schedules of assessments. suspected or known drug abuse in the 5 years preceding enrollment. 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.