Scientists have been working toward an HIV vaccine since 1984. It’s done from two angles: An empirical approach that quickly moves vaccine candidates into human testing, and a theoretical approach that designs vaccine candidates based on an understanding of the immune response to the infection, according to the National Institute of Allergy and Infectious Diseases. In July, it was reported that a treatment, which aims to provide immunity against various strains of the virus, produced an anti-HIV immune system response in tests on 393 people.