Impact of increased antiretroviral therapy use during the treatment as prevention era in Australia.

Background. We analysed the impact of increased antiretroviral therapy (ART) on HIV epidemiology and healthcare costs in Australia during the 'Treatment-as-prevention' and 'Undetectable equals Untransmissible (U=U)' eras. Methods. We conducted a retrospective modelling analysis between 2009 and 2019 to calculate the potential impact of early initiation of ART and treatment-as-prevention on HIV among gay and bisexual men (GBM). The model incorporates the change in the proportion diagnosed, treated, and virally suppressed, as well as the scale-up of oral HIV pre-exposure prophylaxis (PrEP) and the change in sexual behaviour during this period. We simulated a baseline and a no ART increase scenario and conducted a costing analysis from a national health provider perspective with cost estimates in 2019 AUD. Results. Increasing ART use between 2009 and 2019 averted an additional 1624 [95% percentile interval (PI): 1220-2099] new HIV infections. Without the increase in ART, the number of GBM with HIV would have increased from 21 907 (95% PI: 20 753-23 019) to 23 219 (95% PI: 22 008-24 404) by 2019. HIV care and treatment costs for people with HIV increased by $296 (95% PI: $235-367) million AUD (assuming no change in annual healthcare costs). This was offset by a decrease in the lifetime HIV costs (with 3.5% discounting) for those newly infected of $458 (95% PI: $344-592) million AUD, giving a net cost saving of $162 (95%: $68-273) million AUD (and a benefits-to-cost ratio of 1.54). Conclusions. Increasing the proportion of Australian GBM on effective ART between 2009 and 2019 likely resulted in substantial reductions in new HIV infections and cost savings. [ABSTRACT FROM AUTHOR]