Although oral PrEP is already used in a handful of countries, a Thursday session on the future of chemoprophylaxis reviewed a swathe of research that has the promise of improving adherence and realising the maximum benefit of PrEP. One presentation looked at the interaction of PrEP and STIs. Do STI’s affect the efficiency of PrEP? Can PrEP reduce STIs through engaging users in screening, care and treatment?n The answers seem to be ‘no’ to the first and ‘yes’ to the second.
Research on topical PrEP, in the form of gels or a vaginal ring, have not shown the promise of oral PrEP, but low adherence may be one explanation, and is a topic for further research. As one researcher remarked, the gruesome applicator could well explain why women in the trial abandoned the whole exercise. Branding and marketing of both oral and topical PrEP will be the key to successful implementation. There are also a whole bunch of trials on rectal microbicides underway, but the question must be asked, why continue with this when oral PrEP is so effective?
Another fascinating branch of studies is looking at long-acting, injectable PrEP. At least three trials are expected to conclude in the next two years - one that involves 8-weekly dosing (after four weeks of oral PrEP to ensure there are no side effects). This drug, Rilpvirine is also being considered for long-acting ART treatment. The fact that this involves an injection so humongous that half has to be given in each buttock, may dent the prospects for this regimen...
New prevention tools and technologies are essential, but so too are new strategies for implementation and monitoring. One session explored the possibility of using ‘prevention cascades’ to improve programming. As we know, the use of a cascade is useful for tracking a longitudinal cohort, for purposes of advocacy and to identify areas where there are big fall-offs and therefore require solutions and/or new ideas. Following the successful use of the treatment cascade to monitor and track progress of antiretroviral therapy, in general, and the UNIAIDS 90-90-90 goals in particular, the question is asked whether we can use a similar approach for HIV prevention
Tracking HIV prevention interventions through a cascade presents many challenges: not the least to define a denominator (who is at risk?) and the incorporation of the full range of prevention tools which are now available. A simple cascade does not allow for the dynamics involved in HIV prevention and, in the era of TasP, treatment is part of the prevention continuum. Other challenges relate to finding the required data on adherence (to prevention options) and identifying an endpoint for the prevention cascade.
Despite these challenges, the presenters provided a possible conceptual framework for the prevention cascade and showed the practical use of a prevention cascade at programme implementation level through a VMMC implementation project in Zimbabwe. At least as an operational tool for now, the prevention cascades provides a novel way to monitor progress in and frame a global call for action for HIV prevention.