* systemic corticosteroids required for chronic conditions at doses \> 0.5mg/kg/day prednisone equivalent within 7 days of enrollment * prior evusheld or other anti-sars cov-2 prophylaxis \< 2 weeks prior to enrollment * therapies that cause profound t-cell or b cell depletion within 30 days of enrollment * maintenance therapies (e.g. rituximab, bruton tyrosine kinase inhibitors, janus kinase inhibitors) within 30 days of enrollment * received investigational or licensed sars-cov-2 vaccines after their qualifying cellular therapy. patients who received a sars- cov-2 vaccine prior to cellular therapy are eligible for this trial, as revaccination for these patients (e.g. flu and shingles vaccine) is standard of care. * received a live vaccine ≤30 days prior to administration 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 the first injection and \> 2 weeks post 2nd injection * history of allergic reactions attributed to compounds of similar chemical or biologic composition to vaccine agents * history of adverse event with a prior smallpox vaccination * any mva vaccine or poxvirus vaccine in the last 12 months * history (suspected or confirmed) of myocarditis or pericarditis * clinically significant uncontrolled illness * females only: pregnant or breastfeeding * any other condition that would, in the investigator's judgment, contraindicate the subject'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) * anyone considered to be in a vulnerable population as defined in 45 cfr §46.111 (a)(3) and 45 cfr §46, subparts b-d

* systemic corticosteroids required for chronic conditions at doses \> 0.5mg/kg/day prednisone equivalent within 7 days of enrollment * prior evusheld or other anti-sars cov-2 prophylaxis \< 2 weeks prior to enrollment * therapies that cause profound t-cell or b cell depletion within 30 days of enrollment * maintenance therapies (e.g. rituximab, bruton tyrosine kinase inhibitors, janus kinase inhibitors) within 30 days of enrollment * received investigational or licensed sars-cov-2 vaccines after their qualifying cellular therapy. patients who received a sars- cov-2 vaccine prior to cellular therapy are eligible for this trial, as revaccination for these patients (e.g. flu and shingles vaccine) is standard of care. * received a live vaccine ≤30 days prior to administration 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 the first injection and \> 2 weeks post 2nd injection * history of allergic reactions attributed to compounds of similar chemical or biologic composition to vaccine agents * history of adverse event with a prior smallpox vaccination * any mva vaccine or poxvirus vaccine in the last 12 months * history (suspected or confirmed) of myocarditis or pericarditis * clinically significant uncontrolled illness * females only: pregnant or breastfeeding * any other condition that would, in the investigator's judgment, contraindicate the subject'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) * anyone considered to be in a vulnerable population as defined in 45 cfr §46.111 (a)(3) and 45 cfr §46, subparts b-d

systemic corticosteroids required for chronic conditions at doses > 0.5mg/kg/day prednisone equivalent within 7 days of enrollment prior evusheld or other anti-sars cov-2 prophylaxis < 2 weeks prior to enrollment therapies that cause profound t-cell or b cell depletion within 30 days of enrollment maintenance therapies (e.g. rituximab, bruton tyrosine kinase inhibitors, janus kinase inhibitors) within 30 days of enrollment received investigational or licensed sars-cov-2 vaccines after their qualifying cellular therapy. patients who received a sars- cov-2 vaccine prior to cellular therapy are eligible for this trial, as revaccination for these patients (e.g. flu and shingles vaccine) is standard of care. received a live vaccine ≤30 days prior to administration 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 the first injection and > 2 weeks post 2nd injection history of allergic reactions attributed to compounds of similar chemical or biologic composition to vaccine agents history of adverse event with a prior smallpox vaccination any mva vaccine or poxvirus vaccine in the last 12 months history (suspected or confirmed) of myocarditis or pericarditis clinically significant uncontrolled illness females only: pregnant or breastfeeding any other condition that would, in the investigator's judgment, contraindicate the subject'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) anyone considered to be in a vulnerable population as defined in 45 cfr §46.111 (a)(3) and 45 cfr §46, subparts b-d

systemic corticosteroids required for chronic conditions at doses > 0.5mg/kg/day prednisone equivalent within 7 days of enrollment prior evusheld or other anti-sars cov-2 prophylaxis < 2 weeks prior to enrollment therapies that cause profound t-cell or b cell depletion within 30 days of enrollment maintenance therapies (e.g. rituximab, bruton tyrosine kinase inhibitors, janus kinase inhibitors) within 30 days of enrollment received investigational or licensed sars-cov-2 vaccines after their qualifying cellular therapy. patients who received a sars- cov-2 vaccine prior to cellular therapy are eligible for this trial, as revaccination for these patients (e.g. flu and shingles vaccine) is standard of care. received a live vaccine ≤30 days prior to administration 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 the first injection and > 2 weeks post 2nd injection history of allergic reactions attributed to compounds of similar chemical or biologic composition to vaccine agents history of adverse event with a prior smallpox vaccination any mva vaccine or poxvirus vaccine in the last 12 months history (suspected or confirmed) of myocarditis or pericarditis clinically significant uncontrolled illness females only: pregnant or breastfeeding any other condition that would, in the investigator's judgment, contraindicate the subject'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) anyone considered to be in a vulnerable population as defined in 45 cfr §46.111 (a)(3) and 45 cfr §46, subparts b-d

- patients who have received second allogeneic hct are not eligible (patients who have undergone a previous autologous hct are eligible - systemic corticosteroids required for chronic conditions at doses > 0.5mg/kg/day prednisone equivalent - patients on maintenance therapies (e.g. rituximab, bruton tyrosine kinase inhibitors, janus kinase inhibitors), who may have significantly attenuated response to vaccination - subjects using investigational or licensed agents that may prevent or treat sars-cov-2 are excluded such as any previous sars-cov-2 vaccine - subjects who have had a live vaccine ≤30 days prior to administration 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 the first injection and > 2 weeks post 2nd injection - history of allergic reactions attributed to compounds of similar chemical or biologic composition to vaccine agents - history of adverse event with a prior smallpox vaccination - any mva vaccine or poxvirus vaccine in the last 12 months - clinically significant uncontrolled illness - females only: pregnant or breastfeeding - any other condition that would, in the investigator's judgment, contraindicate the subject'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) - anyone considered to be in a vulnerable population

- patients who have received second allogeneic hct are not eligible (patients who have undergone a previous autologous hct are eligible - systemic corticosteroids required for chronic conditions at doses > 0.5mg/kg/day prednisone equivalent - patients on maintenance therapies (e.g. rituximab, bruton tyrosine kinase inhibitors, janus kinase inhibitors), who may have significantly attenuated response to vaccination - subjects using investigational or licensed agents that may prevent or treat sars-cov-2 are excluded such as any previous sars-cov-2 vaccine - subjects who have had a live vaccine ≤30 days prior to administration 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 the first injection and > 2 weeks post 2nd injection - history of allergic reactions attributed to compounds of similar chemical or biologic composition to vaccine agents - history of adverse event with a prior smallpox vaccination - any mva vaccine or poxvirus vaccine in the last 12 months - clinically significant uncontrolled illness - females only: pregnant or breastfeeding - any other condition that would, in the investigator's judgment, contraindicate the subject'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) - anyone considered to be in a vulnerable population