Possible HIV Prevention Therapy Shows Promise, But At a Significant Cost

February 11, 2009 • Science Update

A therapy that shows promise in preventing HIV infection could significantly reduce the risk of HIV infection among high-risk groups, but the cost may be substantial unless drug costs can be reduced, according to a study published online ahead of print February 4, 2009, in Clinical Infectious Diseases. The study, which analyzed the risk reduction and probable costs associated with the treatment using a computer model simulation, was co-funded by NIMH, the National Institute of Allergy and Infectious Diseases, and the National Institute of Drug Abuse.

An HIV prevention strategy currently under study involves giving high-risk populations antiretroviral drug regimens to protect them from HIV infection in case they are exposed to the virus, an approach known as pre-exposure prophylaxis (PrEP). The method involves the combination of two antiretroviral medications—tenofovir and entricitabine—which has shown promise in preliminary studies. David Paltiel, Ph.D., of Yale University and colleagues devised a computer model to assess PrEP's potential success in reducing HIV infection rates among a population that is at high risk of contracting HIV. For the simulation, the researchers targeted one such group—men who have sex with men. They assumed an average age of 34, a 1.6 percent HIV infection rate per year, and the use of PrEP at a cost of $9,000 per year. They also assumed the treatment would prevent HIV infection at a rate of 50 percent.

Among the test population, the lifetime HIV infection risk decreased from 44 percent to 25 percent, and the average life expectancy increased from 39.9 to 40.7 years. However, using the initial model assumptions, lifetime treatment costs increased from $81,000 to $232,700, an increase that would exceed most standards of cost-effectiveness of health interventions. The researchers found that with small improvements in effectiveness, reductions in treatment costs, or by targeting the treatment to a younger, higher-risk population, PrEP might be as cost-effective as other widely recommended public health and medical interventions.

According to the researchers, this is the first model to establish performance benchmarks that could help researchers understand the circumstances under which PrEP would provide improved patient care, better public health outcomes and increased financial value. If the costs of the treatment can be reduced, PrEP could be a good option for reducing the rate of HIV infection among high risk populations.

PrEP represents a promising approach to containing the HIV epidemic, but this analysis focused only on the United States. Future research should take into account the potential impact of PrEP on a global scale. In addition, future research will need to determine the most appropriate criteria for who is eligible to receive PrEP.

Paltiel DA, Freedberg KA, Scott CA, Schackman BR, Losina E, Wang B, Seage GR, Sloan CE, Sax PE, Walensky RP. HIV preexposure prophylaxis in the US: Impact on lifetime infection risk, clinical outcomes and cost effectiveness . Clinical Infectious Diseases. Published online ahead of print Feb. 4, 2009.