 There is no vaccine yet to stop the spread of HIV, but an antiviral tested in Africa to stop new infections in young women has had remarkable results. In over 2,000 young women, we did not see a single HIV infection, which, even as I tell you that today, that kind of makes the hair on my arms go up because we just have never seen this before. So it's 100% effective. Could this halt the AIDS pandemic? The question on Science in Action, coming up.