“After two years of analyzing the results of the largest AIDS vaccine clinical trial ever held — called RV144 — researchers say they have found two ways the immune system can respond, which could predict whether those inoculated will be protected or are more likely to become infected with HIV,” CNN’s health blog “The Chart” reports. The results were presented at the AIDS Vaccine 2011 conference being held this week in Bangkok, Thailand (Young, 9/13).

The large study, which concluded in 2009 in Thailand, showed that during the first year of vaccination, protection was as high as 60 percent but it quickly declined to 31 percent overall, BMJ notes (Roehr, 9/15). According to PlusNews, “Vaccine recipients with high levels of one type of antibody response had the lowest rate of HIV infection, and those with high levels of another type had the highest rate of infection.” Barton Haynes of Duke University, who coordinated the follow-up study of the trial data, said the information is a “hypothesis generator” that would inform future research, PlusNews reports (9/14).