Healthy adults aged 18–55 years

Willingness to allow the investigators to discuss the volunteer's medical history with the volunteer's HIV lead physician (and GP, if appropriate)

HIV antibody positive; diagnosed at least 6 months previously

CD4 count >350; nadir CD4 not <300

HIV viral load not > 100 000 copies/ml

Written informed consent

Any clinically significant abnormal finding on screening biochemistry or haematology blood tests or on urinalysis

Any antiretroviral therapy within the past 6 months

Any AIDS-defining illness

Chest x ray showing tuberculosis or evidence of other active infection

Prior receipt of a recombinant MVA or Fowlpox vaccine

Use of any investigational or non-registered drug, live vaccine or medical device other than the study vaccine within 30 days preceding dosing of study vaccine, or planned use during the study period

Administration of chronic (defined as more than 14 days) immunosuppressive drugs or other immune modifying drugs within 6 months of vaccination (for corticosteroids, this will mean prednisolone, or equivalent, ≥0.5 mg/kg/day; inhaled and topical steroids are allowed)

History of allergic disease or reactions likely to be exacerbated by any component of the vaccine—for example, egg products

Presence of any underlying disease that compromises the diagnosis and evaluation of response to the vaccine (including evidence of cardiovascular disease, history of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ), history of insulin requiring diabetes mellitus, any ongoing chronic illness requiring ongoing specialist supervision (eg, gastrointestinal), and chronic or active neurological disease)

History of ≥2 hospitalisations for invasive bacterial infections (pneumonia, meningitis)

Suspected or known current drug and/or alcohol abuse (as defined by an alcohol intake of >42 units a week)

Seropositive for hepatitis B surface antigen and/or hepatitis C antibodies

Evidence of serious psychiatric condition

Any other ongoing chronic illness requiring hospital specialist supervision

Administration of immunoglobulins and/or any blood products within the 3 months preceding the planned administration of the vaccine candidate

Pregnant/lactating female and any female who is willing or intends to become pregnant during the study

Any history of anaphylaxis in reaction to vaccination

Principal investigator assessment of lack of willingness to participate and comply with all requirements of the protocol, or identification of any factor felt to significantly increase the participant's risk of suffering an adverse outcome