* known current sars cov-2 infection * prior evusheld or other anti-sars cov-2 prophylaxis \< 2 weeks prior * prior hematopoietic cell transplantation (hct) or chimeric antigen receptor (car) t cell therapy within the previous year * systemic corticosteroids required for chronic conditions at doses \> 0.5mg/kg/day prednisone equivalent within 7 days of enrollment * intensive cytotoxic therapies, t-cell depleting therapies, within 30 days of enrollment; however, patients with stable disease on maintenance therapies are allowed (see conmeds for lists of acceptable and contraindicated therapies) * participants who have had a live vaccine =\< 30 days prior to administration of any dose of study vaccine or subjects who are =\< 2 weeks within administration of inactivated vaccines (e.g., influenza vaccine). flu shots are allowed \> 2 weeks before a study vaccine injection and \> 2 weeks post study vaccine injection * history of allergic reactions attributed to compounds of similar chemical or biologic composition to study agent (e.g., egg allergies) * active infection not controlled on appropriate therapy * history of adverse event with a prior smallpox vaccination * history of pericarditis or myocarditis * any mva vaccine or poxvirus vaccine in the last 12 months * females only: pregnant or breastfeeding * any other condition that would, in the investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures * prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)

* known current sars cov-2 infection * prior evusheld or other anti-sars cov-2 prophylaxis \< 2 weeks prior * prior hematopoietic cell transplantation (hct) or chimeric antigen receptor (car) t cell therapy within the previous year * systemic corticosteroids required for chronic conditions at doses \> 0.5mg/kg/day prednisone equivalent within 7 days of enrollment * intensive cytotoxic therapies, t-cell depleting therapies, within 30 days of enrollment; however, patients with stable disease on maintenance therapies are allowed (see conmeds for lists of acceptable and contraindicated therapies) * participants who have had a live vaccine =\< 30 days prior to administration of any dose of study vaccine or subjects who are =\< 2 weeks within administration of inactivated vaccines (e.g., influenza vaccine). flu shots are allowed \> 2 weeks before a study vaccine injection and \> 2 weeks post study vaccine injection * history of allergic reactions attributed to compounds of similar chemical or biologic composition to study agent (e.g., egg allergies) * active infection not controlled on appropriate therapy * history of adverse event with a prior smallpox vaccination * history of pericarditis or myocarditis * any mva vaccine or poxvirus vaccine in the last 12 months * females only: pregnant or breastfeeding * any other condition that would, in the investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures * prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)

known current sars cov-2 infection prior evusheld or other anti-sars cov-2 prophylaxis < 2 weeks prior prior hematopoietic cell transplantation (hct) or chimeric antigen receptor (car) t cell therapy within the previous year systemic corticosteroids required for chronic conditions at doses > 0.5mg/kg/day prednisone equivalent within 7 days of enrollment intensive cytotoxic therapies, t-cell depleting therapies, within 30 days of enrollment; however, patients with stable disease on maintenance therapies are allowed (see conmeds for lists of acceptable and contraindicated therapies) participants who have had a live vaccine =< 30 days prior to administration of any dose of study vaccine or subjects who are =< 2 weeks within administration of inactivated vaccines (e.g., influenza vaccine). flu shots are allowed > 2 weeks before a study vaccine injection and > 2 weeks post study vaccine injection history of allergic reactions attributed to compounds of similar chemical or biologic composition to study agent (e.g., egg allergies) active infection not controlled on appropriate therapy history of adverse event with a prior smallpox vaccination history of pericarditis or myocarditis any mva vaccine or poxvirus vaccine in the last 12 months females only: pregnant or breastfeeding any other condition that would, in the investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)

known current sars cov-2 infection prior evusheld or other anti-sars cov-2 prophylaxis < 2 weeks prior prior hematopoietic cell transplantation (hct) or chimeric antigen receptor (car) t cell therapy within the previous year systemic corticosteroids required for chronic conditions at doses > 0.5mg/kg/day prednisone equivalent within 7 days of enrollment intensive cytotoxic therapies, t-cell depleting therapies, within 30 days of enrollment; however, patients with stable disease on maintenance therapies are allowed (see conmeds for lists of acceptable and contraindicated therapies) participants who have had a live vaccine =< 30 days prior to administration of any dose of study vaccine or subjects who are =< 2 weeks within administration of inactivated vaccines (e.g., influenza vaccine). flu shots are allowed > 2 weeks before a study vaccine injection and > 2 weeks post study vaccine injection history of allergic reactions attributed to compounds of similar chemical or biologic composition to study agent (e.g., egg allergies) active infection not controlled on appropriate therapy history of adverse event with a prior smallpox vaccination history of pericarditis or myocarditis any mva vaccine or poxvirus vaccine in the last 12 months females only: pregnant or breastfeeding any other condition that would, in the investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)