The participation of people from diverse ethnic backgrounds is essential to our understanding of how a vaccine will work throughout the world. Rejection from one study does not automatically disqualify a volunteer from other studies. The effects of the drugs being tested are not fully known. The vaccine might produce pain, tenderness, redness or swelling at the injection site, or perhaps mild flu-like symptoms. Often, the recipient feels no side effects at all.
Every drug is tested for many years to watch for possible side effects.
No, you cannot. The vaccines include only genetically engineered copies of HIV proteins or HIV genes, designed to stimulate a response in your immune system. No one can be HIV-infected by the vaccine. There is, as yet, no vaccine to prevent HIV infection. That's what these trials are all about.