The PEDVAC study is the first trial designed to analyze safety and immunogenicity of a therapeutic vaccination with a multiclade multigene HIV DNA vaccine (HIVIS) in infected children. Twenty HIV-1 vertically infected children (6-16 years of age), on stable antiretroviral treatment for at least 6 months with HIV-1 RNA<50 copies/ml and stable CD4 counts (> 400 cells/mm³ or 25%) over 12 months of follow-up, were recruited into the study. Enrolled patients have been randomized into two arms: a control group of 10 children who continued previous antiretroviral treatment (HAART) (arm A) and a group of 10 children immunized intramuscularly with the HIVIS DNA vaccine in addition to previous HAART (arm B). Immunizations took place at week 0, 4, 12 and the boosting dose is planned at week 36. The 10 children in the vaccine group have received the first 3 priming doses of the HIVIS vaccine. Safety data showed good tolerance to the vaccination schedule. Mild cutaneous self-limeted reactions consisted of local irritation, usually itching or erythema +/- swelling at the injection site, were reported. No severe systemic adverse events have been observed. No vaccinated children had a decrease of CD4 T-cell counts from baseline. None experienced virological failure. Analysis of cellular immune responses was scheduled at week 0, 4, 12, 16, 20, 40, 60, 72 and 96 by standard lymphoproliferation assay, intracellular cytokine staining and cell-ELISA, a miniaturized assay to measure antigen-induced IFNγ secretion. Evaluation of these results is in progress and will provide key information on the status and changes of antigen specific immunity during HIV DNA immunization.