Detailed results of the now-famous Thai AIDS vaccine trial confirmed that the vaccine is modestly effective, but hinted that its effect may fade over time. The vaccine reduced the risk of HIV infection by between 26% and 31.2%, depending on how the study population was analyzed, according to Nelson Michael, MD, PhD, of the Walter Reed Army Institute of Research in Rockville, Md.

Vaccination programs against H1N1 swine flu are under way in the United States, China and Australia and will begin soon in parts of Europe. As people await their chance for immunization, here are some questions and answers about flu symptoms and what to do if they arrive before the vaccine does.

For the first time, an experimental vaccine has prevented infection with the AIDS virus, a watershed event in the deadly epidemic and a surprising result. Recent failures led many scientists to think such a vaccine might never be possible.