An effective HIV vaccine may need to prompt strong responses from immune cells called CD8+ T cells to protect people from acquiring HIV, according to a new study. The study findings draw comparisons between the immune system activity of past HIV vaccine study participants and people with HIV who naturally keep the virus from replicating even in the absence of antiretroviral therapy (ART). The latter individuals are often called ‘long-term non-progressors’ or ‘elite controllers’ (LTNPs/ECs).