A study has shown that twice-yearly injections of a drug used to treat AIDS have been 100% effective in preventing new HIV infections in young women. The new injections could be especially important for the fight against HIV in parts of the developing world, like in Cape Town, South Africa, one of the locations for the trial. South Africa has the highest number of people living with HIV in the world. (AP video: Wesley Fester; Production: Sebabatso Mosamo)