French researchers have reported a case of a 59-year--old HIV-positive participant in a therapeutic vaccine trial who transmitted the virus to his monogamous female partner during a planned interruption of his antiretroviral (ARV) treatment. The trial randomized participants to receive injections of a pair of experimental vaccines or a placebo over a 24-week period. At the study’s outset, participants were all on ARVs, had a fully suppressed viral load for at least 18 months and had a CD4 count above 600. Their ARV treatment was interrupted between week 36 and 48 of the trial, during which time they received monitoring and safer-sex counseling every two weeks. The man, whom investigators appraised as quite knowledgeable about HIV, experienced chronic depression—for which he declined treatment—and also had poorly managed diabetes. After one month off ARVs, he developed a viral load of 2,000, a figure that ultimately peaked at 16,000. During this time, his partner seroconverted.