What is the potential of ‘Treatment for Prevention’ in fighting HIV/AIDS?

UNAIDS 90:90:90 appears to have set the course for a global ‘treatment as prevention’ strategy. In 2015 the US revised its National HIV/AIDS Strategy (NHAS) to harmonize its goals with UNAIDS 90% targets for testing, engagement in care, and virological suppression. Though the HIV/AIDS community have been nervous about the impact of the recent change of administration, the expenditure underpinning the NHAS has been retained despite 18% cuts to the Department of Health and Human Services budget (Trump and HIV/AIDS spending).

It is no doubt with a view to maintaining this political course that Borre & Walensky have recently sought to quantify the benefits of the revised goals as against ‘current pace’ by using mathematical simulation to project five- and twenty-year outcomes. Given the disproportionate implication of black MSM in these effects (they face a 50% lifetime risk of infection), outcomes are given for this group as well as for the US at large.

These outcomes are impressive. Achieving NHAS targets, as against current pace, will cause rates of transmission over twenty years to decline: across the general population, from 2.8 to 1.7 per 100 person years (PY); among blacks MSM from 4.3 to 2.7. This will result in a decrease in deaths from 750,000 to 551,000. Cost-effectiveness, as against current pace, is estimated at $68,000 per Quality Adjusted Life Year (QALY) over the whole population, and at $38,300 per QALY for black MSM – though the authors point to the high proportion of costs represented by the ART drugs, and the potential for improvement in cost-effectiveness, if there were a significant reduction in ART cost. As for affordability, NHAS revised targets would require only a 3% per year increase in budgetary allocation.

UNAIDS 90:90:90 represents an altogether more ambitious – and, arguably, less realistic – target in medium- or limited-resource settings. Some have cautioned against the advocacy of ‘treatment for prevention’ (TfP) as a global single plank intervention strategy – and on two counts. First, Kielmann & Cataldo/STI and Wringe & Renju/STI warn that the evaluation of success in terms of TfP targets can result in the adoption of short term or culturally inappropriate measures that could have long-term implications for public attitudes towards care providers. For example, the greater status often accorded to patient-experts in inadequately resourced contexts can result in the promotion of culturally regressive attitudes that may be counter-productive in the long-term business of establishing proper engagement in care (see ‘More haste less speed’/STI/blogs).

Griensven & Lo/STI oppose TfP on altogether more radical grounds. With the MSM populations of the cities of the Asia-Pacific region, they argue, infection is so acute and transmission so rapid that any TfP-based intervention is doomed to be ineffective: HIV will have been widely disseminated before linkage-to-care can take place. Needless to say, this critique of TfP goes along with advocacy in the case of these populations of an approach that ‘widens the cascade with a preventive extention’ – that is to say, PrEP.