INO-4201 as Booster in Healthy VSV-ZEBOV Vaccinees

1. Has provided written informed consent prior to screening
2. Males and females ≥ 18 years old
3. Previously vaccinated with a single dose of VSV-ZEBOV at any dose between 10\^5 and 10\^8 pfu more than 6 months prior to inclusion
4. Free of clinically significant health problems, as determined by pertinent medical history and clinical examination at study screening
5. Has an acceptable site for ID electroporation considering the deltoid and anterolateral quadriceps muscles
6. Is post-menopausal, or surgically sterile, or has a partner who is sterile, or uses a medically effective contraception with a failure rate of \<1% per year when used consistently and correctly from screening until 6 months following last dose.

Exclusion Criteria:

1. Female volunteers who are pregnant or breastfeeding at screening or prior to dosing
2. Administration of an investigational compound either currently or within 30 days of Day 0
3. Prisoner or volunteers who are compulsorily detained (involuntary incarceration) for treatment of either a physical or psychiatric illness
4. Active drug or alcohol or substance abuse or dependence
5. Planned administration of another Ebola vaccine (including rVSV-ZEBOV and Ad26/MVA-BN-Filo vaccines) during the study period
6. Administration of a live vaccine in the 21 days or an inactivated vaccine in the 14 days before planned injection
7. Current or anticipated concomitant immunosuppressive therapy (excluding inhaled, topical skin and/or eye drop-containing corticosteroids, or low-dose methotrexate). Systemic corticosteroids must be discontinued at least 4 weeks prior to first dose.

Temporary exclusion criteria:

1. Acute disease at the time of randomization
2. Active skin lesions at the potential injection site
3. Temperature ≥38.0°C at the time of randomization
4. Recent receipt of a SARS-CoV-2 vaccine with final dose \<4 weeks prior