50 Top 10 Lists of 2007

Top 10 Medical Breakthroughs

#1. Circumcision Can Prevent HIV

In December 2006, the National Institutes of Health halted two clinical trials of male circumcision after an early review of the data showed that the procedure dramatically reduced transmission of HIV. Early this year, the details of those studies were published in the Lancet: In the two randomized trials, which included 7,780 HIV-negative men in Rakai, Uganda, and Kisumu, Kenya, researchers found that medically circumcised men were at least 51% less likely than uncircumcised men to acquire HIV during sex with women. The editors of the Lancet called the discovery "a new era for HIV prevention." Scientists don't know yet whether male circumcision can also provide protection for female partners — a new study on the hypothesis is forthcoming next year.

Connect to this TIME Story