Modeling Does the Math to Add Up Impacts of HIV Answers in the Works

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.

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