HIV Treatments as Prevention (TasP) by Seth C. Kalichman

Author:Seth C. Kalichman
Language: eng
Format: epub
Publisher: Springer New York, New York, NY

Antiretroviral therapies are the great success in the story of AIDS. There are now several classes of medications to disrupt every point of HIV’s replication cycle. When used in combinations, these medications impede the virus’ ability to infect immune cells. Treatment has improved the health and extended the lives of millions of people.

The potential for these potent drugs to also prevent HIV transmission is not a new idea. Even in the late 1980s it was known that AZT accumulated at therapeutic levels in the genital tract. But it was not until 1994 when the true potential for treatment to prevent HIV transmission was realized. The AIDS Clinical Trial Group protocol 076 demonstrated that treating HIV-infected pregnant women with AZT significantly reduced the risk of infecting newborns [105]. Heralded as what remains the single greatest breakthrough in HIV prevention, the use of antiretroviral therapies during labor and delivery has saved countless children from HIV infection. The success of treatment in preventing perinatal HIV transmission also forms the basis for exploiting the potential for treatments to prevent the sexual transmission of HIV.

One driving force behind the enthusiasm for TasP is that it uses an available and proven strategy against HIV. With treatments showing remarkable clinical efficacy for people living with HIV, interest in TasP grew greater with every failed vaccine and microbicide. Failure to scale-up effective behavioral interventions also left a vacuum for prevention interventions. Just as Roger Tatoud’s model discussed earlier suggests that the pressure for an effective prevention technology escalated as attempts fell flat. Reductions in the cost of treatments also make scaling-up TasP economically feasible, at least in resource-rich countries. Treatments have also become less toxic, better tolerated, and available with simpler dosing. Finally, mathematical models have forecasted the potential for significant impacts of TasP on HIV in developing countries. Even prior to a solid empirical foundation, mathematical models of TasP got the attention of policy makers, pushing the research agenda forward.

In addition to its promise, TasP also poses great challenges. The National AIDS Trust Panel in the UK raised several questions about the potential use of TasP [106]. First there are the realities of scaling-up HIV testing, which many see as a precondition for impactful TasP. HIV testing, however, remains low in many high-risk populations. There are also serious questions about just how often individuals who remain at high risk can and should be tested. There are also challenges to TasP presented by acute HIV infection and the potential for persons to falsely test HIV negative in the acute infection stages. Long-term treatment adherence also poses a serious obstacle to TasP. Failure to adhere to medication regimens allows HIV to replicate, undermining the entire strategy. With treatment failure comes risks for developing treatment-resistant strains of virus, which can be transmitted. Even under optimal adherence, viral suppression is not always durable in the long run. Also, viral suppression in blood plasma does not necessarily mean that HIV is suppressed in the genital compartment. There are also concerns about the impact of treatment perceptions and beliefs on sexual and drug use behaviors.

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