Calculating PrEP's Capacity to Prevent HIV in the Real World

Published: October 28, 2014

Original Article:

Researchers have devised a model to estimate the number of men who have sex with men (MSM) who would have to be taking Truvada as pre-exposure prophylaxis (PrEP) in order to prevent one HIV infection; the model also calculated the cost per additional quality-adjusted life-year (QALY) gained among the treated population. The investigators published their findings from various simulations in the journal PLOS ONE. They note that the clinical- and cost-effectiveness of PrEP varies dramatically.

One QALY is the equivalent of an additional year of life lived in perfect health. However, if that year is compromised by less than perfect health, the number is designated as somewhere between zero and one. For each HIV infection prevented in this study, 2.24 QALYs were gained.

The researchers characterized MSM populations in the models according to various risk factors for contracting HIV, including PrEP adherence, condom use, sexual frequency, the prevalence of HIV in the population, and the use of antiretroviral (ARV) therapy among HIV-positive people in the population. For PrEP’s base-case efficacy, the researchers looked to the results of the iPrEx study, which found that PrEP’s population-level efficacy was 44 percent.

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