Association for Public Policy Analysis & Management

The Centers for Disease Control and Prevention (CDC) estimate that 1.2 million people in the United States are at high risk of acquiring HIV. Most of this population is composed of men who have sex with men (MSM). In July 2012, the U.S. Food and Drugs Administration (FDA) approved the use of Truvada among HIV negative people as a way to reduce the risk of sexually acquired HIV-1 in adults at high risk.Since then it has been known as Truvada for PrEP (Pre-exposure prophylaxis), or just PrEP. PrEP consists of taking one pill a day, and it should be used in combination with safer sex practices. In this paper, I study how the availability of PrEP is affecting users’ romantic relationships and sexual practices, and if this change in behavior has a causal effect on the increase in sexually transmitted diseases (STDs) seen in the United States in the last years. Using data from NSFG and NHANES, and a propensity score matching differences-in-differences approach, I find evidence of risk compensation after the introduction of PrEP. I first document an increase in the probability of having more than 2 sexual partners in the last year as well as having a new sex partner in the last 12 months. I do not find evidence of an increase in sexual activity, however. This increase in the number of sexual partners translates into a large increase in the probability of having a non-monogamous relationship and a not statistically significant decrease in the probability of being married or cohabitating. Then, I study risky sexual behavior, specifically the probability of no using condoms, finding a large increase in condomless sexual activity. I document individuals switching from always using condoms and using condoms less than 50% of the times to never using condoms. I find a large and significant increase in the probability of being tested for any STD of 10 percentage points. I also provide suggestive evidence of an increase in STDs (chlamydia and HPV).