Modeling does the math to add up impacts of HIV answers in the works

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What if, about a decade from now, a vaccine that reduced the risk of getting HIV by 70 percent in everyone who received it was ready for roll-out in countries where it’s needed most? What if the antiretroviral PrEP, or pre-exposure prophylaxis, known to be effective now against acquiring HIV, became widely available in a long-acting form to the population with the highest rate of new infections, and the biggest barriers to daily adherence — young women and teenage girls — in South Africa? That they would lower rates of ongoing HIV transmission and prevent illnesses and deaths already drives the development of both interventions, but in times of competing demands on diminishing dollars, two recently released modelling exercises look beyond that goal, to quantify  specifically the public health and economic returns of investments in saving lives.

Exploring the Potential Health Impact and Cost-Effectiveness of AIDS Vaccine within a Comprehensive HIV/AIDS Response in Low- and Middle-Income Countries, released Tuesday on PLOS One comes from International AIDS Vaccine Initiative, AVAC and Avenir Health through support from USAID. It examines not only the value of a future vaccine, but also how many moving parts of existing interventions — from funding and future developments to how currently effective answers continue to remain out of reach for those most marginalized — affect outcomes of efforts now. In 2014, the report notes, two million people got HIV. The report concludes that a vaccine rolled out in 2027 would have a meaningful impact on dropping rates of new infections under a variety of scenarios — including under a continuation of current responses, if current investments were accelerated to just half of what UNAIDS has recommended, and if they were accelerated fully. In the last case, the modeling finds, a vaccine that with three doses offers five years of 70 percent reduced risk of acquiring HIV in everyone who took it would — if widely accepted — lower what would otherwise be already reduced annual rates of new infections by 44 percent by 2037, by 65 percent over the following two-and-a-half decades, and by 78 percent, to 122,000 by 2070. The impact of the vaccine would be greater, the article notes, if other interventions are not fully accelerated.

A paper released in the Journal of Infectious Diseases last month looked, in a more limited context, at an intervention likely to be available sooner. Potential Clinical and Economic Value of Long-Acting Preexposure Prophylaxis for South African Women at High-Risk for HIV Infection, by a team of researchers led by Dr. Rochelle Walensky of the Meidal Practice Evaluation Center of Massachussetts General Hospital’s Division of Infectious Disease, looks at the possibility of increased use, but also added costs if a proven method was accessible in a form adapted to young women’s needs. Even in the face of improved HIV treatment coverage, the report of the findings notes, HIV infections among South African teenage girls in South Africa remain on the rise, with young women and girls in the country, a commentary accompanying the report says, facing more than 60 percent lifetime odds of getting the virus. At the same time, trials that include VOICE — Vaginal and Oral Interventions to Control the Epidemic — have found young women least likely to maintain a daily prevention regimen. The modeling, then, looks at PrEP formulations designed to be administered every two to three months. Among the findings — the cost of long-acting pre-exposure prophylaxis against HIV would for each infection prevented, roughly double the cost of one person’s lifetime care, but be offset in the long term by overall lowered costs of treatment as a result of lowered overall transmissions. Noting the need for effective HIV prevention measures until all people who need treatment for HIV receive it, the authors recommend tackling both the present — with education on, and access to pre-exposure prophylaxis in its current forms, as well as expanded research to develop long-acting PrEP.

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