Johnson & Johnson says its potential HIV vaccine did not provide protection against the virus in a study of young women in sub-Saharan Africa. J&J plans to end that study. But researchers will continue a separate, late-stage trial involving a different composition of the vaccine in men and transgender people. The study in sub-Saharan Africa involved about 2,600 women who were deemed to be at high risk of acquiring HIV, which causes AIDS. Participants were randomly selected to receive either the vaccine or a placebo, and researchers found that the vaccine was only 25% effective at preventing HIV.