Abstract
OBJECTIVE: Government-imposed physical distancing restrictions during the COVID-19 pandemic disrupted biobehavioral HIV prevention practices and access to healthcare services. This study aimed to use a mathematical model to evaluate the impact of COVID-19 on the HIV epidemic among MSM in Australia, using empirical data. DESIGN: A retrospective modeling study. METHODS: We developed a mathematical model to estimate monthly HIV incidence between January 2020 and August 2022. We obtained aggregated monthly data for sexual partners, condom use, HIV testing, preexposure prophylaxis (PrEP) use, and migration. Three scenarios were simulated: a COVID-19 scenario; a no COVID-19 scenario where input parameters remained at pre-COVID-19 values; and a no COVID-19 scenario with continued PrEP scale-up. RESULTS: In the absence of the COVID-19 pandemic, 1263 (95% percentile interval: 880-1706) infections would have occurred between January 2020 and August 2022 compared to 915 (95% percentile interval: 638-1282) for the COVID-19 scenario (a 27.6% reduction). Reduced sexual partners was the leading factor contributing to the change in HIV infections and diagnoses (-24.9 and -10.6%, respectively). MSM aged at least 50 years had a larger reduction (31.0%) in new HIV infections than their younger counterparts (19.9%). CONCLUSION: A substantial reduction in new HIV infections and diagnoses in Australia occurred during the COVID-19 pandemic, largely due to decreased numbers of sexual partners. This reduction underscores the need for sustained public health strategies leveraging reduced transmission rates to continue progress toward eliminating HIV in Australia.