Optimising HIV pre-exposure prophylaxis and testing strategies in men who have sex with men in Australia, Thailand, and China: a modelling study and cost-effectiveness analysis

Background: Men who have sex with men (MSM) in the Asia-Pacific region have a disproportionately high burden of HIV infection compared with the general population. Although pre-exposure prophylaxis (PrEP) for HIV is highly effective at preventing new HIV infections, the cost-effectiveness of PrEP for MSM in different countries in the AsiaPacific region with varying PrEP coverage and HIV testing frequencies remains unstudied. We aimed to analyse the economic and health benefits of long -acting injectable cabotegravir (CAB -LA) compared with oral PrEP in highincome countries and low-income and middle-income countries within the Asia-Pacific region. Methods: We developed a decision-analytic Markov model to evaluate the population impact and cost-effectiveness of PrEP scale-up among MSM in Australia, Thailand, and China. We assumed a static cohort of 100 000 MSM aged 18 years or older who were at risk of HIV infection, with a monthly cycle length over a 40-year time period. We evaluated hypothetical scenarios with universal PrEP coverage of 80% among 100 000 suitable MSM in each country. We modelled oral PrEP and CAB -LA for MSM with diverse HIV testing frequency strategies. We adopted the healthcare system's perspective with a 3% annual discount rate. We calculated the incremental cost-effectiveness ratio (ICER), measured as additional cost per quality-adjusted life-year (QALY) gained, to compare different strategies with the status quo in each country. All costs were reported in 2021 US$. We also performed one-way, two-way, and probabilistic sensitivity analyses to assess the robustness of our findings. Findings: Compared with the status quo in each country, expanding oral PrEP to 80% of suitable MSM would avert 8 center dot 1% of new HIV infections in Australia, 14 center dot 5% in Thailand, and 26 center dot 4% in China in a 40-year period. Expanding oral PrEP use with 6-monthly HIV testing for both PrEP and non-PrEP users was cost-saving for Australia. Similarly, expanding oral PrEP use remained the most cost-effective strategy in both Thailand and China, but optimal testing frequency varied, with annual testing in Thailand (ICER $4707 per QALY gained) and 3-monthly testing in China (ICER $16 926 per QALY gained) for both PrEP and non-PrEP users. We also found that replacing oral PrEP with CAB -LA for MSM could avert more new HIV infections (12 center dot 8% in Australia, 27 center dot 6% in Thailand, and 32 center dot 8% China), but implementing CAB -LA was not cost-effective due to its high cost. The cost of CAB -LA would need to be reduced by 50-90% and be used as a complementary strategy to oral PrEP to be cost-effective in these countries. Interpretation: Expanding oral PrEP use for MSM, with country-specific testing frequency, is cost-effective in Australia, Thailand, and China. Due to the high cost, CAB -LA is currently not affordable as a single -use strategy but might be offered as an additional option to oral PrEP.