Assessing HIV acquisition risks among men who have sex with men in the United States of America.

Men who have sex with men (MSM) can reduce their risk of acquiring human immunodeficiency virus (HIV) by using various prevention strategies and by understanding the effectiveness of each option over the short- and long-term. Strategies examined were: circumcision; insertive anal sex only; consistent, 100% self-reported condom use; and pre-exposure prophylaxis (PrEP). PrEP efficacy was based on three levels of adherence. The cumulative HIV acquisition risk among MSM over periods of 1 year and 10 years were estimated with and without single and combinations of prevention strategies. A Bernoulli process model was used to estimate risk. In the base case with no prevention strategies, the 1-year risk of HIV acquisition among MSM was 8.8%. In contrast, the 1-year risk associated with circumcision alone was 6.9%; with insertive sex only, 5.5%; with 100% self-reported condom use, 2.7%; and with average, high, and very high PrEP adherence, 5.1%, 2.5%, and 0.7%, respectively. The 10-year risk of HIV acquisition among MSM with no prevention strategy was 60.3%. In contrast, that associated with circumcision alone was 51.1%; with insertive sex only, 43.1%; with 100% self-reported condom use, 24.0%; and with average, high, and very high PrEP adherence, 40.5%, 22.2%, and 7.2%, respectively. While MSM face substantial risk of HIV, there are now a number of prevention strategies that reduce risk. Very high adherence to PrEP alone or with other strategies appears to be the most powerful tool for HIV prevention.