The study will be a two center, randomized, double blind, placebo controlled study of the MVA MERS S_DF-1 candidate delivered by i.m. injection. To evaluate the MERS-S-specific antibody responses and safety profile induced by the two dosage levels of MVA-MERS-S_DF-1 the data will be compared to a placebo control group.

This will be a Phase Ib, two-center study in approximately 160 healthy adults aged 18-55 years

The study is separated in two parts:

Part A:

The study starts with a single center open-label run-in phase of two dose levels (cohort 1 "low dose": 2x10^7 PFU, cohort 2 "high dose": 2x10^8 PFU) in 10 healthy subjects. 5 subjects will be allocated to each dose cohort and will receive immunization on day 0 and day 28.

Part B:

Two-center, randomized, double-blind, placebo-controlled, dose-finding study. This part is a double-blinded trial in approximately 150 healthy subjects. Subjects will be allocated to two different dose cohorts and a placebo cohort; each receiving three vaccine injections.

Inclusion Criteria:

1. Written informed consent form.
2. Healthy male and female subjects aged 18-55 years.
3. No clinically significant acute health problems as determined from medical history and physical examination at screening visit.
4. Body mass index 18.5 - 30.0 kg/m2 and weight > 50 kg at screening.
5. Non-pregnant, non-lactating female with negative pregnancy test.
6. Males and females who agree to comply with the applicable contraceptive requirements of the protocol.

Exclusion Criteria:

1. Receipt of any vaccine from 2 weeks prior to each trial vac-cination (4 weeks for live vaccines) to 3 weeks after each trial vaccination.
2. Receipt of vaccination against MERS or MVA immunizations.in the medical history.
3. Known allergy to the components of the MVA-MERS-S_DF-1 vaccine product.
4. Evidence in the subject's medical history or in the medical examination that might influence either the safety of the subject or the absorption, distribution, metabolism or excretion of the investigational product.
5. Any confirmed or suspected immunosuppressive or immuno-deficient condition, cytotoxic therapy in the previous 5 years, and/or diabetes.
6. Any chronic or active neurologic disorder, including seizures and epilepsy, excluding a single febrile seizure as a child.

Double-blinded