New Prevention Strategy May Significantly Reduce HIV Infections

The risk of HIV infection in high-risk populations may be substantially reduced by an antiretroviral drug treatment currently being tested in clinical trials, according to a study led by a researcher at the Yale School of Public Health.

The study examined the costs and benefits of giving antiretroviral drug regimens to high-risk populations in order to protect them from HIV infection, a prevention strategy known as pre-exposure prophylaxis (PrEP). Investigators created a mathematical model that focused on homosexual men of a mean age of 34. They estimated that PrEP would reduce lifetime HIV infection risk in these populations from 44 percent to 25 percent while increasing their overall life expectancy from 39.9 to 40.7 years.

Conservative assumptions were built into the team’s model: that PrEP is only 50 percent effective and that it costs $9,000 annually.

A. David Paltiel, a professor in the division of Health Policy Administration and the study’s lead author, said the model is the first to establish performance benchmarks of the clinical, epidemiologic and economic potential of PrEP. The drug regimen is being formally tested in several ongoing clinical trials.

“In light of the many disappointments of HIV prevention efforts in recent years, our results strongly support further development of PrEP-based approaches to controlling the epidemic,” Paltiel said.

At a cost of $9,000 a year, the treatment is not cost effective by U.S. standards. However, Paltiel’s model also predicts that if a cheaper therapy were given to a younger population or those with a higher annual risk of HIV infection, PrEP would be as cost-effective as other widely recommended public health and medical interventions.

The team’s analysis also found that if PrEP’s effectiveness turns out to be higher than estimated in the model, the reduction in lifetime infection risk would be even more dramatic. If the drug achieves 90 percent efficacy, the risk of infection would drop from 44 percent to 5.8 percent.

Details of the research, to be published in the March 15 issue of Clinical Infectious Diseases, are currently available on the journal’s website. The National Institute of Mental Health, the National Institute of Allergy and Infectious Diseases, the National Institute on Drug Abuse and the Doris Duke Charitable Foundation sponsored the study. Other study authors are: Kenneth A. Freedberg, Callie A. Scott, Paul Sax, Caroline Sloan, Bingxia Wang and Rochelle P. Walensky of Massachusetts General Hospital; Bruce R. Schackman of Weill Cornell Medical College; Elena Losina of Boston University School of Public Health; and George R. Seage III of Harvard School of Public Health.

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