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No HIV infections from partners with fully suppressed viral load during long-term follow up of landmark treatment as prevention trial
Keith Alcorn, 2015-07-21 04:20:00

Final follow up of the HPTN 052 study of treatment as prevention shows no evidence of HIV transmission from people with fully suppressed viral load to their partners, four years after the first results from the study demonstrated that early HIV treatment reduced the risk of HIV transmission by 96%. These results were presented by Professor Myron Cohen at the 8th International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention in Vancouver on Monday.

Describing the results as “the final word” from HPTN 052, Professor Cohen, of the University of North Carolina at Chapel Hill, presented a final intent-to-treat analysis of the study, which demonstrated in 2011 that early antiretroviral treatment greatly reduced the risk of HIV transmission to serodiscordant partners. The study compared the rates of transmission between two study arms: a deferred treatment arm, in which people diagnosed with HIV started treatment at a CD4 count of 250 cells/mm3 or if they developed an AIDS-defining illness prior to reaching this threshold; and an immediate treatment arm, in which people with CD4 cell counts in the range 350-550 cells/mm3 started treatment immediately. The interim analysis showed a 96% reduction in the risk of HIV transmission.

The final intent-to-treat analysis reported on 1,763 couples, of which 1,171 (66%) remained in follow up (603 of 886 in the immediate treatment arm and 568 of 877 in the deferred treatment arm). The study accumulated 9822 person-years of follow up of HIV-positive participants.

A total of 36 infections that could be genetically linked to the index partner took place during the study up until the time of the interim analysis in 2011, one in the early treatment arm and 36 in the deferred arm. This represented a 97% risk reduction.

After the interim analysis and the offer of antiretroviral therapy to all participants in the deferred treatment arm, a total of nine genetically linked infections occurred: two in the early arm and seven in the deferred arm. This represented a 72% risk reduction, but overall, the risk reduction associated with early treatment was 93%. Professor Cohen said that intent-to-treat analysis represents a conservative estimate of efficacy, pointing to the fact that infections which occurred after treatment had been started had occurred when viral load was not fully suppressed.