Inclusion Criteria:  Written informed consent. Healthy male and female adults aged 18 - 64 at time of informed consent. Body mass index 18.5 - 32.0 kg/m2 and weight > 50 kg at screening. Female participants: non-pregnant, non-lactating with negative pregnancy test. Females who agree to comply with the applicable contraceptive requirements of the protocol. ≥ 6 months fully vaccinated with a (conditionally)licensed mRNA vaccine against COVID-19 (Part B only)  Exclusion Criteria:  Receipt of any vaccine from 4 weeks prior to each trial vaccination (8 weeks for live vaccines) to 6 weeks after each trial vaccination. Previous rMVA immunization. Previous immunization with investigational vaccine against COVID-19. Previous immunization with EUA/conditionally licensed vaccine against COVID-19 (not applicable to Part B). Evidence of active SARS-CoV-2 infection Known allergy to the components of the MVA-SARS-2-ST vaccine product or history of life-threatening reactions to vaccine containing the same substances. Known history of anaphylaxis to vaccination or any allergy likely to be exacerbated by any component of the trial vaccines. Evidence in the participant's medical history or in the medical examination that might influence either the safety of the participant or the absorption, distribution, metabolism or excretion of the investigational product. Clinically relevant findings in ECG or significant thromboembolic events in medical history. Any confirmed or suspected immunosuppressive or immunodeficient condition, cytotoxic therapy in the previous 5 years, and/or uncontrolled diabetes (HbA1c ≥ 7.0). Any known chronic or active neurologic disorder, including seizures and epilepsy, excluding a single febrile seizure as a child.