A study shows that a twice-yearly shot was 100% effective in preventing new HIV infections in women in Africa. The shot is already used in the U.S. and elsewhere as a treatment for the virus that causes AIDS, and drugmaker Gilead is testing it for prevention. In a study of 5,000 young women and girls, there were no infections in those who got the shots. Roughly 2% of a group who were given daily prevention pills ended up catching HIV from infected sex partners. The shot is also being tested in men. The company-funded research was released Wednesday.
