Although science is known for being a forward-looking field, researchers have found that they can often benefit from a glance over their shoulders. By combining an experimental AIDS vaccine with a long-neglected molecule called poly-IC, scientists discovered that they were able to significantly improve its effectiveness. Their new, bolstered vaccine not only stimulated the production of HIV-attacking immune cells in mice, but also allowed the rodents to maintain immunity over a significantly longer period of time. The immunity-directing dendritic cell has long been viewed as a potent resource for vaccine researchers: If they can direct a piece of a pathogen directly to the cell, it should be able to instruct other immune cells to react to the invader.