The study, called HVTN-505, was begun in 2009, over the years enrolling over 2,500 volunteers. The vaccination process doesn't actually involve any live or even deactivated HIV; instead, it starts with one that includes genetic material that's simply modeled after the virus, to prime the immune system. Then comes the real vaccine, involving recombinant DNA (meaning, DNA from various sources) based on adenovirus type 5, a common cold virus that in this case has been disabled so it doesn't actually cause a cold. Attached to those adenoviruses are artificial versions of HIV antigens. Antigens--the term is short for antibody generator--trigger an immune response, and these artificial antigens were designed to attack the three major HIV subtypes.