A Study of a New Vaccine Against Two Types of Ebola

Inclusion Criteria: 1. Healthy adults aged 18 to 55 years. 2. Able and willing (in the Investigator's opinion) to comply with all study requirements. 3. Willing to allow confirmation of their past medical history either through: provision of a GP medical record summary, allowing investigators to obtain a copy of their medical history from their GP practice or by providing an alternative acceptable means of confirming their past medical history. 4. Agreement to refrain from blood donation during the course of the study. 5. Provide written informed consent. 6. For women of childbearing potential only: Willingness to practice continuous effective contraception for the duration of the trial. 7. For women of childbearing potential only: A negative pregnancy test on the day of both screening and vaccination. Exclusion Criteria: 1. Participation in another research study involving receipt of an investigational product in the 30 days preceding enrolment or during the trial follow up period. 2. Receipt of a recombinant simian adenoviral vaccine prior to enrolment. 3. Planned receipt of another adenoviral vectored vaccine (e.g. Oxford/AstraZeneca or Janssen COVID-19 vaccines) within 90 days after the vaccination with the ChAdOx1 biEBOV. 4. Planned or actual receipt of any vaccines administered within 30 days (before or after) enrolment and/or planned receipt of a vaccine ≤30 days after enrolment EXCEPT for protein, RNA (or other non-adenovirus based) COVID-19 vaccinations which may be given within 14 days of the trial vaccine. 5. Previous receipt of an Ebolavirus vaccine. 6. Administration of immunoglobulins and/or any blood products within the three months preceding the planned administration of the vaccine candidate. 7. Any confirmed or suspected immunosuppressive or immunodeficient state, including HIV infection; asplenia; recurrent, severe infections and chronic (more than 14 days) systemically active immunosuppressant medication within the past 6 months. 8. History of allergic disease or reactions likely to be exacerbated by any component of the vaccine. Including hypersensitivity to the active substance or to any of the excipients of the IMP or Vaxzevria (i.e. the Oxford/AstraZeneca COVID-19 vaccine). 9. History of hereditary angioedema, acquired angioedema, or idiopathic angioedema. 10. History of anaphylaxis in relation to vaccination. 11. History of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ). 12. History of serious psychiatric condition likely to affect participation in the study. 13. Ongoing or planned pregnancy or breastfeeding during the trial follow up period. 14. Bleeding disorder (eg. Factor deficiency, coagulopathy or platelet disorder), or prior history of significant bleeding or bruising following IM injections or venepuncture. 15. History of confirmed major thrombotic event (including cerebral venous sinus thrombosis, deep vein thrombosis, pulmonary embolism), history of antiphospholipid syndrome, or history of heparin induced thrombocytopenia. 16. Individuals who have experienced thrombosis with thrombocytopenia syndrome (TTS) following vaccination with Vaxzevria (i.e. the Oxford/AstraZeneca COVID-19 vaccine). 17. Individuals who have previously experienced episodes of capillary leak syndrome. 18. Any other serious chronic illness requiring hospital specialist supervision. 19. Suspected or known current alcohol abuse as defined by an alcohol intake of greater than 42 units every week. 20. Suspected or known injecting drug abuse in the 5 years preceding enrolment. 21. Detectable circulating hepatitis B surface antigen (HBsAg). 22. Seropositive for hepatitis C virus (antibodies to HCV). 23. Any clinically significant abnormal finding on screening biochemistry or haematology blood tests or urinalysis. 24. Any other significant disease, disorder or finding which may significantly increase the risk to the volunteer because of participation in the study, affect the ability of the volunteer to participate in the study or impair interpretation of the study data.