Key components of Ending the HIV Epidemic (EHE) plan include increasing HIV antiretroviral therapy (ART) and HIV pre-exposure prophylaxis (PrEP) coverage. One complication to addressing this service delivery challenge is the wide heterogeneity of HIV burden and health care access across the United States. It is unclear how the effectiveness and efficiency of expanded PrEP will depend on different baseline ART coverage.
We used a network-based model of HIV transmission for men who have sex with men (MSM) in San Francisco. Model scenarios increased varying levels of PrEP coverage relative under current empirical levels of baseline ART coverage and 2 counterfactual levels. We assessed the effectiveness of PrEP with the cumulative percentage of infections averted (PIA) over the next decade and efficiency with the number of additional person-years needed to treat (NNT) by PrEP required to avert one HIV infection.
In our projections, only the highest levels of combined PrEP and ART coverage achieved the EHE goals. Increasing PrEP coverage up to 75% showed that PrEP effectiveness was higher at higher baseline ART coverage. Indeed, the PIA was 61% in the lowest baseline ART coverage population and 75% in the highest. The efficiency declined with increasing ART (NNT range from 41 to 113).
Improving both PrEP and ART coverage would have a synergistic impact on HIV prevention even in a high baseline coverage city such as San Francisco. Efforts should focus on narrowing the implementation gaps to achieve higher levels of PrEP retention and ART sustained viral suppression.