"A paper published in Nature [on Monday] sheds light on how a vaccine can turn the immune system against [HIV] and so offer protection from infection," Nature News reports, noting "[t]he results are also being presented at the AIDS Vaccine 2012 conference in Boston, Massachusetts, this week" (Callaway, 9/10). Previous results from a trial called RV144 showed that two vaccines, Sanofi's Alvac and VaxGen's Aidsvax, reduced the risk of HIV infection by 31 percent over three years when used together, compared with people who received a placebo, according to Bloomberg (Bennett, 9/10). Last year, researchers showed "that those who responded to the vaccine and fended off HIV tended to produce antibodies against a specific part of the virus's protein shell called the V1/V2 loop," Nature News writes, adding, "The study published [Monday] goes a stage further, showing that the people who were vaccinated yet still contracted HIV had been infected by viruses that had mutations in the V2 portion."