A Study to Evaluate the Safety of the HIV-1 Vaccine MVA-B in Chronic HIV-1 Infected Patients Successfully Treated With HAART

Inclusion Criteria: * Patient is ≥ 18 years of age; * Voluntarily signed informed consent; * Patient is male, or female with negative pregnancy test prior to enrolment; * Patient has a proven HIV-1 infection (with positive antibodies against HIV-1 and a detectable plasma HIV-1 RNA); * Patient must be on stable treatment with HAART for at least 6 months (HAART is defined as an antiretroviral regimen consisting of at least three registered antiretroviral agents\*); * Mean of all measured CD4+ cell counts during the 6 months prior to the start of HAART must be above or equal to 200 cells/ mm3 * Current CD4+ cell count must be at least 450 cells/ mm3; * HIV-RNA must be below 50 copies/ mL for the last 6 months prior to inclusion, during at least two measurements (occasional so called 'blips' up to 50 copies/mL are permitted); * Patient is one of the following: not sexually active, or a heterosexually active female, agreeing to use condoms with her partner from 14 days prior to the first vaccination until 4 months after the last, even though using another method of contraception, and willing to undergo pregnancy tests during screening and prior to each vaccination, or a male, agreeing to use condoms with his partner from the day of the first vaccination until 4 months after the last vaccination. Exclusion Criteria: * Treatment with a non-HAART regimen of antiretroviral agents prior to the start of HAART; * History of a CDC class C event (see Appendix); * Interruption of HAART during the course of the study which is expected at the time of inclusion; * History of exposure \<20 years ago to any poxvirus based vaccine; * Patient is female and has a positive pregnancy test or the wish of pregnancy: * Active opportunistic infection, or any active infection or malignancy within 30 days prior to screening visit; * Therapy with immunomodulatory agents, including cytokines (e.g. IL2) and gamma globulin, or cytostatic chemotherapy within 90 days prior to screening visit; * History of allergy to any vaccine component; * Use of anti-coagulant medication; * Use of any investigational drug during the 90 days prior to study entry; * Previous failure to antiretroviral and/or mutations conferring genotypic resistance to antiretroviral therapy * Any other condition which, in the opinion