* participation in trials of prophylactic drugs for covid-19 during the course of the study; note: participation in covid-19 treatment trials is permitted in case of hospitalization due to covid-19, after confirmation of positive pcr. the study team should be informed as soon as possible. participants with covid-19 not hospitalized with positive pcr results for covid-19 may be medicated according to standard clinical practice. * participation in sars-cov-2 serological research where participants are informed of their serological status during the course of the study; * planned receipt of any vaccine (authorized or investigational), within 30 days before and after vaccination; * prior receipt of an investigational vaccine or authorized with the possibility of impacting the interpretation of the study data (for example, vaccines vectorized by adenovirus, any vaccines against coronavirus); * administration of immunoglobulins and/or any blood products in the three months prior to the planned administration of the candidate vaccine; * any confirmed or suspected immunosuppressive or immunodeficiency state; asplenia; severe recurrent infections and chronic use (more than 14 days) of immunosuppressive medication in the last 6 months, except for topical steroids or short-term oral steroids (cycle lasting ≤14 days); * history of allergic disease or reactions possibly exacerbated by any component of chadox1 ncov-19 or menacwy or paracetamol; * any history of angioedema; * any history of anaphylaxis; * pregnancy, lactation or willingness/intention to become pregnant during the study; * current diagnosis or treatment for cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ); * history of severe psychiatric illness that possibly affects your participation in the study; * hemorrhagic disorder (for example, factor deficiency, coagulopathy or platelet disorder), or a previous history of significant bleeding or bruising after im injections or venipuncture; * current suspected or known dependence on alcohol or drugs; * severe and/or uncontrolled cardiovascular diseases, respiratory diseases, gastrointestinal diseases, liver disease, kidney disease, endocrine disorder, and neurological disease (mild/moderate well-controlled comorbidities are allowed); * history of covid-19 confirmed by laboratory; * seropositive for antibodies to sars-cov-2 before recruitment; this exclusion criteria does not apply to participants enrolled from version 4.0 of the protocol onwards * continued use of anticoagulants, such as coumarins and related anticoagulants (for example, warfarin) or new oral anticoagulants (for example, apixaban, rivaroxaban, dabigatran and edoxaban); * any other significant illness, disorder or finding that may significantly increase the risk for the participant, affect his/her ability to participate in the study or impair the interpretation of the study data. re-vaccination exclusion criteria (two-dose groups only) * anaphylactic reaction following administration of vaccine * pregnancy

* participation in trials of prophylactic drugs for covid-19 during the course of the study; note: participation in covid-19 treatment trials is permitted in case of hospitalization due to covid-19, after confirmation of positive pcr. the study team should be informed as soon as possible. participants with covid-19 not hospitalized with positive pcr results for covid-19 may be medicated according to standard clinical practice. * participation in sars-cov-2 serological research where participants are informed of their serological status during the course of the study; * planned receipt of any vaccine (authorized or investigational), within 30 days before and after vaccination; * prior receipt of an investigational vaccine or authorized with the possibility of impacting the interpretation of the study data (for example, vaccines vectorized by adenovirus, any vaccines against coronavirus); * administration of immunoglobulins and/or any blood products in the three months prior to the planned administration of the candidate vaccine; * any confirmed or suspected immunosuppressive or immunodeficiency state; asplenia; severe recurrent infections and chronic use (more than 14 days) of immunosuppressive medication in the last 6 months, except for topical steroids or short-term oral steroids (cycle lasting ≤14 days); * history of allergic disease or reactions possibly exacerbated by any component of chadox1 ncov-19 or menacwy or paracetamol; * any history of angioedema; * any history of anaphylaxis; * pregnancy, lactation or willingness/intention to become pregnant during the study; * current diagnosis or treatment for cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ); * history of severe psychiatric illness that possibly affects your participation in the study; * hemorrhagic disorder (for example, factor deficiency, coagulopathy or platelet disorder), or a previous history of significant bleeding or bruising after im injections or venipuncture; * current suspected or known dependence on alcohol or drugs; * severe and/or uncontrolled cardiovascular diseases, respiratory diseases, gastrointestinal diseases, liver disease, kidney disease, endocrine disorder, and neurological disease (mild/moderate well-controlled comorbidities are allowed); * history of covid-19 confirmed by laboratory; * seropositive for antibodies to sars-cov-2 before recruitment; this exclusion criteria does not apply to participants enrolled from version 4.0 of the protocol onwards * continued use of anticoagulants, such as coumarins and related anticoagulants (for example, warfarin) or new oral anticoagulants (for example, apixaban, rivaroxaban, dabigatran and edoxaban); * any other significant illness, disorder or finding that may significantly increase the risk for the participant, affect his/her ability to participate in the study or impair the interpretation of the study data. re-vaccination exclusion criteria (two-dose groups only) * anaphylactic reaction following administration of vaccine * pregnancy

- participation in trials of prophylactic drugs for covid-19 during the course of the study; note: participation in covid-19 treatment trials is permitted in case of hospitalization due to covid-19, after confirmation of positive pcr. the study team should be informed as soon as possible. participants with covid-19 not hospitalized with positive pcr results for covid-19 may be medicated according to standard clinical practice. - participation in sars-cov-2 serological research where participants are informed of their serological status during the course of the study; - planned receipt of any vaccine (authorized or investigational), within 30 days before and after vaccination; - prior receipt of an investigational vaccine or authorized with the possibility of impacting the interpretation of the study data (for example, vaccines vectorized by adenovirus, any vaccines against coronavirus); - administration of immunoglobulins and/or any blood products in the three months prior to the planned administration of the candidate vaccine; - any confirmed or suspected immunosuppressive or immunodeficiency state; asplenia; severe recurrent infections and chronic use (more than 14 days) of immunosuppressive medication in the last 6 months, except for topical steroids or short-term oral steroids (cycle lasting ≤14 days); - history of allergic disease or reactions possibly exacerbated by any component of chadox1 ncov-19 or menacwy or paracetamol; - any history of angioedema; - any history of anaphylaxis; - pregnancy, lactation or willingness/intention to become pregnant during the study; - current diagnosis or treatment for cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ); - history of severe psychiatric illness that possibly affects your participation in the study; - hemorrhagic disorder (for example, factor deficiency, coagulopathy or platelet disorder), or a previous history of significant bleeding or bruising after im injections or venipuncture; - current suspected or known dependence on alcohol or drugs; - severe and/or uncontrolled cardiovascular diseases, respiratory diseases, gastrointestinal diseases, liver disease, kidney disease, endocrine disorder, and neurological disease (mild/moderate well-controlled comorbidities are allowed); - history of covid-19 confirmed by laboratory; - seropositive for antibodies to sars-cov-2 before recruitment; this exclusion criteria does not apply to participants enrolled from version 4.0 of the protocol onwards - continued use of anticoagulants, such as coumarins and related anticoagulants (for example, warfarin) or new oral anticoagulants (for example, apixaban, rivaroxaban, dabigatran and edoxaban); - any other significant illness, disorder or finding that may significantly increase the risk for the participant, affect his/her ability to participate in the study or impair the interpretation of the study data. re-vaccination exclusion criteria (two-dose groups only) - anaphylactic reaction following administration of vaccine - pregnancy

- participation in trials of prophylactic drugs for covid-19 during the course of the study; note: participation in covid-19 treatment trials is permitted in case of hospitalization due to covid-19, after confirmation of positive pcr. the study team should be informed as soon as possible. participants with covid-19 not hospitalized with positive pcr results for covid-19 may be medicated according to standard clinical practice. - participation in sars-cov-2 serological research where participants are informed of their serological status during the course of the study; - planned receipt of any vaccine (authorized or investigational), within 30 days before and after vaccination; - prior receipt of an investigational vaccine or authorized with the possibility of impacting the interpretation of the study data (for example, vaccines vectorized by adenovirus, any vaccines against coronavirus); - administration of immunoglobulins and/or any blood products in the three months prior to the planned administration of the candidate vaccine; - any confirmed or suspected immunosuppressive or immunodeficiency state; asplenia; severe recurrent infections and chronic use (more than 14 days) of immunosuppressive medication in the last 6 months, except for topical steroids or short-term oral steroids (cycle lasting ≤14 days); - history of allergic disease or reactions possibly exacerbated by any component of chadox1 ncov-19 or menacwy or paracetamol; - any history of angioedema; - any history of anaphylaxis; - pregnancy, lactation or willingness/intention to become pregnant during the study; - current diagnosis or treatment for cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ); - history of severe psychiatric illness that possibly affects your participation in the study; - hemorrhagic disorder (for example, factor deficiency, coagulopathy or platelet disorder), or a previous history of significant bleeding or bruising after im injections or venipuncture; - current suspected or known dependence on alcohol or drugs; - severe and/or uncontrolled cardiovascular diseases, respiratory diseases, gastrointestinal diseases, liver disease, kidney disease, endocrine disorder, and neurological disease (mild/moderate well-controlled comorbidities are allowed); - history of covid-19 confirmed by laboratory; - seropositive for antibodies to sars-cov-2 before recruitment; this exclusion criteria does not apply to participants enrolled from version 4.0 of the protocol onwards - continued use of anticoagulants, such as coumarins and related anticoagulants (for example, warfarin) or new oral anticoagulants (for example, apixaban, rivaroxaban, dabigatran and edoxaban); - any other significant illness, disorder or finding that may significantly increase the risk for the participant, affect his/her ability to participate in the study or impair the interpretation of the study data. re-vaccination exclusion criteria (two-dose groups only) - anaphylactic reaction following administration of vaccine - pregnancy