How safe are HIV vaccine trials?
Most vaccine trials study HIV-negative people. The vaccine is to protect people form HIV infection, and so the people studied cannot already be infected with HIV. These trials do not put people at risk of catching HIV, because the vaccine being used is not a full live virus.
(Adapted from a question from the i-Base Q&A pages of the African Eye a new treatment publication for African communities affected by HIV who are living in the UK)