Inclusion Criteria:  Documented informed consent of the participant Age >=18 years Eastern Cooperative Oncology Group (ECOG) =< 2 Allogeneic or autologous hematopoietic cell transplant (HCT), cellular therapy (chimeric antigen receptor [CAR] T-cell) recipients who are at >= 3 months of infusion date of respective regimen Platelets >= 50,000/mm^3 (to be performed within 30 days prior to day 0 of protocol therapy unless otherwise stated) White blood cells (WBCs) >= 1000/mm^3 (to be performed within 30 days prior to day 0 of protocol therapy unless otherwise stated) Total bilirubin < 1.5 X upper limit of normal (ULN) (to be performed within 30 days prior to day 0 of protocol therapy unless otherwise stated) Aspartate aminotransferase (AST) < 2.5 X ULN (to be performed within 30 days prior to day 0 of protocol therapy unless otherwise stated) Alanine aminotransferase (ALT) < 2.5 X ULN (to be performed within 30 days prior to day 0 of protocol therapy unless otherwise stated) Creatinine < 1.5 X ULN (to be performed within 30 days prior to day 0 of protocol therapy unless otherwise stated) Women of childbearing potential (WOCBP): negative urine or serum pregnancy test (to be performed within 30 days prior to day 0 of protocol therapy unless otherwise stated). If the urine pregnancy test is inconclusive a serum pregnancy test will be required  Agreement by females and males of childbearing potential* to use an effective method of birth control or abstain from heterosexual activity for the course of the study through at least 6 weeks after the last dose of protocol therapy  Childbearing potential defined as not being surgically sterilized (men and women) or have not been free from menses for > 1 year (women only)  Exclusion Criteria:  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