Impact and Cost-Effectiveness of Simplified HIV Monitoring and Vertical Transmission Interventions in Papua New Guinea

Although the rollout of antiretroviral therapy initially stabilised the HIV epidemic in Papua New Guinea (PNG), the number of new HIV infections has increased in recent years. The country faces ongoing challenges: limited healthcare infrastructure, high levels of drug-resistant HIV, and elevated rates of vertical (mother-to-child) transmission. Many of these challenges are common to other resource-limited settings. Mathematical modelling is a powerful tool for simulating the epidemic and projecting the impact and cost-effectiveness of various interventions. In Chapter 2, I described a compartmental model to evaluate the impact of several scenarios of scaling up point-of-care (POC) viral load (VL) and drug resistance (DR) testing in PNG adults with HIV. DR testing to confirm treatment failure (and to switch antiretroviral regimen) and DR testing before treatment initiation were considered. Modelling results showed that scaling up point-of-care VL testing could significantly improve key outcomes, including VL suppression, new infections, and the number of people experiencing treatment failures. The model was calibrated to available national epidemiological and UNAIDS modelling estimates. It can also be recalibrated quickly to emerging evidence to support the ongoing implementation of interventions for PNG. Using this model, I presented in Chapter 3 the cost-effectiveness of these scenarios of scaling up POC VL and DR testing. Scaling up DR testing to confirm treatment failure alongside POC VL testing was more cost-effective than either POC VL alone or POC VL alongside DR testing before treatment initiation. Additionally, the modelling showed that a more sustainable implementation period of VL and DR testing of 30 years was more cost-effective than shorter periods of 15 and 10 years. In Chapter 4, I presented cost-effectiveness results from a decision-analytic model of several interventions against vertical transmission of HIV in PNG. A combination of interventions consisting of increased HIV maternal testing with treatment, increased infant post-exposure prophylaxis and implementing early infant diagnosis was comparatively the most cost-effective option. Chapter 5 concludes the thesis by highlighting the public health significance of these findings to the evolving HIV epidemic in PNG. These mathematical models will be valuable tools in guiding sustained HIV response efforts in Papua New Guinea and other similar settings.