TAIPAN Study: Treatment-as-Prevention Cuts HIV Incidence by 66% in Australian GBM

Decade-long Australian study found treatment-as-prevention cut HIV incidence by 66% among GBM, with PrEP boosting the effect.

TAIPAN Study Overview

The TAIPAN longitudinal cohort study utilized routine health record data from 69 health services providing HIV diagnosis and care to gay and bisexual men (GBM) in Australia's two most populous states, New South Wales and Victoria. Data were collected from January 1, 2010, to December 31, 2019, encompassing both HIV-positive and HIV-negative cohorts with a total sample size of 101,772 participants. This extensive dataset enabled direct measurement of HIV incidence and tracking of changes over time.

Key Findings on Viral Suppression and HIV Incidence

The TAIPAN study revealed several key findings that underscore the effectiveness of treatment-as-prevention:

Increase in Viral Suppression: From 2010 to 2019, the population prevalence of viral suppression (defined as plasma HIV viral load <200 RNA copies/µL) increased from 69.27% to 88.31%.

Decrease in HIV Incidence: Over the same period, HIV incidence among GBM decreased from 0.64 per 100 person-years to 0.22 per 100 person-years, representing a 66.37% reduction in new HIV infections.

Correlation Between Viral Suppression and HIV Incidence: A significant association was found: a 1% increase in population viral suppression corresponded with a 6% decrease in HIV incidence (incidence rate ratio [IRR] 0.94, 95% CI 0.93–0.96; p<0.0001).

Introduction and Impact of PrEP: Pre-Exposure Prophylaxis (PrEP) was introduced in 2016, with uptake rising from 17.60% to 36.38% by 2019. After PrEP introduction, the relationship between viral suppression and HIV incidence became even stronger (IRR 0.80, 95% CI 0.70–0.93; p=0.0030), indicating a synergistic effect.

Comprehensive Strategies Driving Success

The success of treatment-as-prevention in these regions is attributed to combined efforts by governments, clinics, and community organizations to remove barriers to antiretroviral therapy (ART)—such as prescribing restrictions and costs—and to expand HIV testing options. Initiatives included express testing, peer-led and community-based testing sites, and rapid diagnostic tests. These efforts significantly increased treatment initiation, sustained viral suppression, and testing rates among GBM.

Challenges and Limitations

The study faced some limitations. The dataset was susceptible to incomplete data, though sensitivity analyses indicated minimal impact on primary findings. It could not account for care outside participating services or in other jurisdictions. The observational design precludes direct causality claims, but behavioral surveys showing declining condom use suggest that changes in sexual practices alone are unlikely to explain the incidence decrease.

Implications for Public Health Policy

The TAIPAN study provides robust evidence that HIV treatment-as-prevention can achieve significant population-level reductions in HIV incidence among GBM. These findings challenge earlier doubts about the public health potential of this approach and emphasize the importance of comprehensive, equitable strategies. For policymakers and healthcare providers, the message is clear: increasing treatment access and reducing undiagnosed infections are vital steps. The combined use of treatment-as-prevention and PrEP, delivered through accessible initiatives, offers a model for other countries.